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Preservation of Audio

by Elizabeth Cohen

The goal of this paper is to focus attention on the practicalities of preserving recorded folk collections. In that spirit, I throw down the gauntlet: the key to preservation is distribution. Moreover, the challenges of preserving recorded folk collections are not primarily technological; they are found in the analog domain and they are mostly aesthetic. The search for the perfect technical solution is a diversion from the painstaking work and art of transfer. If anything, budgetary and acoustopolitical issues hamper our progress in doing what must be done: migrating the collections into the digital domain. A corollary to this is to migrate the collections into the digital domain with uncompromised fidelity.1

Let me digress with an anecdote. A few months back, I spoke with a curator who was deeply concerned about the problems that continue to paralyze us in preserving audio information: the need to preserve materials in their original format; the obsolescence of playback machinery; the risk, in the digital realm, of being unable to define a faithful copy. The discussion took the form of the litany, “Computers are unreliable, the risk of loss is too great, mediums change too quickly, the costs are too high, we can’t even play back our recordings (digital audio tapes, VHS, beta, 8-tracks) from two years ago. We need our temperature- and humidity-controlled storage for original tapes, media with 100­200 year life expectancy, invincible encryption, unlitigatable no-thrash copyright access.” Feeling mischievous, I asked, “What controls the thermostats in your intelligent, climate-controlled conservation room?” My question was met with silence, and I had to suggest that in all likelihood it was a microprocessor: one of those pesky computers was leading the chain of command and was fundamentally responsible for preservation. To be practical, we must recognize that there is no escaping the role and rule of computer technology in the preservation of recorded folk collections. The first hurdle is to recognize the absolute integration of the computer and the computer network into twenty-first century life.

Although it may fall to some of us to deal with the “what ifs” of an electromagnetic pulse tragedy, our collections are far more likely to survive the scars of mayhem if they are robust and alive in many hands. Moreover, to delay the transfer of analog media into the digital domain until it has reached perfection and reliability is to compromise preservation. The more time that passes, the more we allow the further degradation of analog materials.

Distribution is the key to preserving audio folklore collections in the twenty-first century. In fact, distribution is preservation. Moreover, this is the type of preservation that keeps the art alive and not sterilized in a glass case in a passive museum setting. Fortunately, in the networked world, distribution is becoming both easier and cheaper. Our technical concern has shifted to studying the best methods of providing efficient access. Do we want multiple server nodes where folklife information is stored or a single location for a master server farm? Will libraries become storage service provider utilities or will they lease space on new electric company-like utilities?

In the networked world, information can be maintained and distributed electronically; it no longer needs to be centrally located. Archives may no longer need to secure information in vaults. Collections may be located in a thousand places. Digitization forces a paradigm change. Librarians are used to thinking that copies are not the real things. The cult of the original is powerful in the world of analog recording, where information was lost with each generation. Today, however, the original digital material may be preserved in its pristine form anywhere and everywhere.

The good news is that it does not take a rocket scientist to make the choices outlined above; the bad news is that we must still contend with the warped strands of technophobia and politics. I find it painful to listen to the liberal archivists’ search for the Holy Grail medium that will never decay and for which they will never have to maintain machines. I find it more painful to listen to the conservatives launch into another paean to analog tape as the only medium we can trust. These polar beliefs are evidence of an unwillingness to face the task of conversion into the digital domain.

There is no choice but to accept that data migration is the only intelligent policy. We know how to do this to exquisitely fine resolution; banks do it every day. Computer companies upgrade with every significant revision of code, and when the hard disk is full-or when cheaper and faster storage capacity is available-they do one thing: copy and transfer their data. Likewise, consumers adapt to technological change. In the twentieth century, 78-rpm records gave way to long-playing records, then CDs, then DVDs; music can now be accessed from streaming and downloading MP3s. The lifespan of consumer physical digital media is estimated to be 5 years or less (Library of Congress 2000). We do not know what the recording medium of choice will be in 10 years, not to mention 20, but we do know that it will facilitate the transmission of, access to, and storage of bits. Therefore, it is necessary to adopt a device-independent policy for the migration of digital audio data based on robust error correction capability.2 The archival modality must have enough depth to render uncompromised audio quality. Today, for this stage of migration, we are assuming capture at 24-bit 192 kilosamples.3

Folklorists must remain vigilant and acquire the budgets for flawless transfers. All the original information must be retained. There is no scientific reason for loss of quality; only sloppiness or value engineering can intervene. Economies of scale can be achieved in a few basic steps:

  • Identify and set priorities for the items to be preserved.
  • Clearly define your technical criteria for the archival master.
  • Recognize that you are in the preservation business and identify your market.
  • Negotiate for group rates with rerecording facilities. This includes recording studios, postproduction facilities, and independent consultants. Negotiate with the various sound unions to establish reasonable rates for small archives and libraries.
  • Demonstrate the size of your industry. Unless there is an accurate inventory, engineers will not invest in the personnel and infrastructure to go into the preservation business. Students will pursue other areas of sound engineering because there is no assurance or awareness of a viable field of endeavor.

All digital audio materials should be preserved through migration before the decay of the built-in error correction. As long as one operates within the error correction envelope, the original material can be restored, copied, and preserved indefinitely with no loss of information. Error correction also makes it feasible to detect degradation before information loss occurs. Standard algorithms and flagging devices that detect and correct information loss already exist.

With this knowledge, it is possible to establish a policy for data migration of digital audio materials. This policy will enable curators to plan for the data migration necessary in the age of digital audio. It will also prevent the growing intractability of our audio archiving problems.

Why We Cannot Afford to Dawdle

One hundred years of sound recording has left us with a legacy of the equivalent of more than 5 petabytes of professionally recorded audio. Libraries are already overwhelmed with preserving everything from cylinders to vinyl. They are drowning in a preservation crisis as they continue to accumulate media in extinct formats and as audio materials proliferate at a pace they are unable to match.

There is no mercy; according to J. A. Moorer of Sonic Solutions, it is estimated that we are distributing terabytes (TB) of new garage band music each day (personal communication, September 28, 2000). Three million new Web pages appear daily, and a growing percentage include streaming audio (Lyons 2000:146). Currently, 4,271 radio stations “broadcast” their signal on the Internet, up from 2,615 stations a year ago and up from a mere 56 in 1996 (BRS Media Inc. 2000). In autumn 2000, Arbitron’s Web site reported that 25 percent of the American population (57 million) had listened to Internet audio; 20 percent (45 million) listened to radio stations online and 13 percent (30 million) listened to Internet-only audio.4 Information appliance companies are initiating music delivery to phones, to personal digital assistants, and into an array of portable entertainment devices.5 Lest you think that 64-kilobit audio is the sole character generator that is stimulating the data storage industry, the surround sound community is creating its own information-rich recordings. With the standard sample rate shifting to 192/96 kHz, 24 bit, and 4.76 GB of audiovisual data per DVD, multichannel audio is swelling the data banks as well. As FedEx Chief Information Officer Robert Carter said, “There is this tidal wave of storage demand coming at us”(Lyons 2000:146).

In the mid-1990s I wrote about the likely appearance of unlimited and ubiquitous bandwidth in my arguments against adopting nontransparent compressed audio for new systems such as high-definition television. In October 2000, EMC Corporation Senior Vice President James Rothnie was quoted in Forbes as saying that by 2005, the world’s bandwidth could grow a millionfold, making it “virtually free and virtually infinite.” Storage, he believes, will follow suit. He estimates that the total capacity sold annually could grow 50-fold in five years, from 200 to 10,000 petabytes-enough to hold the text of 500,000 Libraries of Congress (Lyons 2000:153).

Storage Media Choices for Customer Use, Interim Storage, and Preservation

Data storage is getting both cheaper and more space efficient. Disk density has nearly doubled every 15 months for the past five years while the cost per megabyte fell 52 percent every year during the same period (Goldman 2000). Today’s 3.5-inch drives are almost 600 times denser than the 14-inch mainframe drives of the 1980s. IBM’s Ultrastar 72ZX holds 73 GB, enough room for every original Frank Sinatra song ever recorded or all of Steven Spielberg’s movies on DVD (Goldman 2000). We are rapidly approaching storage capacity of 1 terabit, or 125 GB per square inch.

The cost per megabyte of storage capacity has decreased from about $30 in 1987 to $0.005 today. Even more remarkable is the decrease in the size of disk drives. In the summer of 2000, IBM released a 1-GB Microdrive for $499. The Microdrive has the dimensions of a matchbook and weighs less than 1 ounce. According to IBM and as reported by Daniel Lyons (2000) in Forbes, its spinning platter, the size of a quarter, can hold the equivalent of 18 CDs. IBM aims to double the storage capacity of the Microdrive every 12 to 18 months. To date, manufacturers of digital cameras, personal digital assistants, and two MP3 players have adopted it.

Current Practice: Tape

Magnetic tape seems to be the interim, if not archival, system currently used for digital storage. Business systems include Exabyte Mammoth-2, Quantum DLT (digital linear tape) 8000, Linear Tape Open, and Sony AIT-2. Tape technology is derived from two branches: helical tape and linear tape. The former is heir to higher density and performance whereas the latter pledges greater reliability.

Many studios are using Exabyte tape drives for a wide range of audio archiving purposes including backup, data transfer, and preservation tasks (Exabyte 1996­2000). I have been told that Abbey Road has more than 2,500 Exabyte tapes. Individual musicians are using both the 8-mm Exabyte tape and the Mammoth M2 225-m tape cartridge formats. For dealing with interim exigencies, Exabyte tape offers advantages: Mammoth-2, for example, uses a two-level Reed-Solomon error correction code. Exabyte’s error correction code corrects errors on the fly by rewriting the blocks within the same track. Data-grade tape, such as AME, stores more data per cartridge. Its anticorrosive properties improve tape durability and reduce tape wear, allowing the media to achieve a 30-year archival rating. Depending on the Exabyte system, reliability ranges between 250,000 and 500,000 hours. This is measured in mean time between failures-the greater the number of hours, the more reliable the drive.

Universal Mastering Studio’s Paul West is currently using Sonic Solutions archiving software on Exabyte tape and thentransferring the content to his mainframe system and onto a Digital Dynamics Processor. However useful Exabyte is as a transfer medium, some users shudder when thinking of it as an archival medium. One user commented, “It seems you can sneeze and lose a file.” From a librarian’s point of view, it is a device that is available only from one company that is extremely vulnerable to the vicissitudes of the stock market. On the other hand, if distribution is preservation, then it is a transfer medium with a potential 30-year lifespan.

Sony Music, under the leadership of David Smith and Malcolm Davidson, has begun transferring Sony Music’s assets into its digital audio archives using an automated tape library system. The archival system consists of a Sun Enterprise 450 server connected by SCSI to SONY DTF tape drives integrated into an ADIC AMI/E automated media server. The design of Sony’s ADIC Automated Media Library is based on the goal of infinite file life, which allows “systematic monitoring and timely replacement of media, with secondary copies, or complete transfer to new technologies”(ADIC 1999). Sony is able to automatically evaluate the quality of the backup tape before it deteriorates. Each cartridge is evaluated regularly by looking at the raw error rates. If the raw error rates grow over time, an exact copy of the tape can be made and the old tape can be deleted. With 600 TB of data on 200,000 cartridges, there was no choice but to automate the error correction (ADIC 1999).

Current Practice: Magneto-optical Disks

Magneto-optical disks may play a role in systems of audio preservation and distribution. They are less expensive than hard disk drives and can provide between 20 and 40 years of viable storage. In the future, blue laser magneto-optical disks will quadruple the amounts of storage capacity.6

The Audio Engineering Society (2000) released its Standard for audio preservation and restorationMethod for estimating life expectancy of magneto-optical (M-O) disks, which is based on effects of temperature and humidity. To develop this standard, a sampling of 80 disks was baseline tested for byte error rate. The standard gives a graph that can be used to estimate the time for a given percentage of disks to fail.

Data Storage Technology: Optical Media

Optical disk material includes CDs, the entire DVD family (DVD, DVD-R, DVD-RW, etc.), and the previously mentioned magneto-optical drives. Use of optical media is extremely convenient and getting more economical every day (DVDs were selling for $.15 to $.19 at the beginning of 2001). However, only 20 years after the commercial birth of the CD are we getting standards about its life expectancy. Pretty absurd!

Standards regarding DVDs are at the initial stage of the drafting process. The good news is that with a little common sense and use of manufacturers’ recommendations, we have a very useful medium for preservation by dissemination.7 If we agree on eternal preservation of contents, then the projected 50-year lifespan of optical media is certainly user friendly (Murray 1994). In addition, manufacturers are listening to the concerns of musicians and music librarians and are offering professional-quality, archival-life disks such as the Kodak Ultima.

However, the lifetime stability of optical disks is not dependent merely on the disk itself. As is clearly covered in the introduction to the draft international standard ISO/DIS 18925.2 Optical Disc Media Storage, it is system and user dependent. Frequent handling, piling, and heat affect CDs and DVDs. In addition to human behavior, the system components include the disk material, equipment on which the disk is run, software, and storage environment. Life expectancy for optical media also depends on light, corrosive gases, and particles.

The National Imagery and Mapping Agency’s National Technology Alliancerecently issued a CD entitled Data Storage Technology Assessment 2000 (Sadashige 2000). Included on the CD are assessments of storage media environmental durability and stability; current state and near-term projections for hardware technology; and a review of magnetic tape, hard disk drives, optical media, optical write-once disks, solid state and emerging technologies, and future possibilities for data storage. “Efforts by the recorder and media manufacturers in the area of data capacity per unit volume improvements are directly transferable to the library (mass media storage system) capability improvements . . . by the year 2005, the floor space requirements for a one petabyte capacity library system may be as small as ten square feet” (Sadashige 2000:5).

Preservation Strategies

The development of successful preservation strategies will require the cooperation of computer scientists, data storage experts, data distribution experts, fieldworkers, librarians, and folklorists. Technology needs to be transferred from the information storage and transportation businesses into the folklife domain. Banking, security, and critical services industries all have dealt with the issue of preserving vital information. We must draw on their experience in developing policies of backup and redundancy and in addressing human interface issues.

The Research and Development Agenda

We need to work with research and development efforts across a variety of disciplines. For example, exciting work is being done in haptic simulation, which someday will allow us to virtually touch and work with virtual objects. We will be able to receive tactile feedback in playing virtual machines or musical instruments.

In conclusion, we have examples from other industries on how to archive. There are no technical barriers to archiving. The technical aspects of this problem have been solved. Capitalism is providing cheaper, faster, and more reliable modes of storing, accessing, and distributing audio. A social decision must be made to migrate materials into the digital domain or it will undoubtedly be done without the aesthetic guidance of the folklife community. The genie is already out of the bottle. If you want a voice, it is time to do the work, not just talk. It is time to approach preservation as a business.


1. Uncompromised fidelity offers several advantages. Innovations in signal processing are heading toward full 3-D image restoration. We should not discard information that may be essential to future sound field reconstruction. The future may offer a way to restore the environment and hence more of the emotional nuances of a recording. Using greater bit depth and higher sampling rates is advantageous. For example, an engineer can raise the level of recorded material without losing resolution, which prevents audible noise from becoming part of a recording. More bits improve the performance of signal processing algorithms by providing more information to work with. This is important for accurate restoration and avoidance of distortion-induced artifacts. There are more intelligent ways to achieve cost savings than compromising on the fidelity of an archival master.

2. Error correction is a well-developed technology that enables detection of signal degradation and enables the user to act before vital information is lost.

3. Some people may think that 192 kilosamples is overkill, but a cohort of researchers and musicians believe that inaudible harmonics may affect brain function. Although I do not think the research is very credible, I believe we should be better safe than sorry. Four times oversampling is a spit in the ocean of bandwidth.

4. Statistics are frequently updated on Arbitron’s Web site:

5. Audio is a key component in the avalanche of new wireless hand-held devices being offered to satisfy consumer demand for mobile broadband music and information. See to-be-published proceedings of “Audio for Information Appliances-Challenges, Solutions, and Opportunities,” March 2001, the Audio Engineering Society,

6. Because blue lasers have shorter wavelengths, it is possible to focus on smaller spots and therefore store more information on optical media.

7. Dissemination is a method of preservation clearly different from preserving an archival master.


ADIC, Inc. 1999. Preserving Musical History: Digital Asset Management for Intellectual Property at Sony Music, Inc. Available from /Sony_Music.pdf.

Audio Engineering Society. 2000. Standard for audio preservation and restorationMethod for estimating life expectancy of magneto-optical (M-O) disks. Available from

BRS Media, Inc. 2000. BRS Media’s Web-Radio Report Strongest Growth Segment of Webcasting Is Radio. Press release, San Francisco, September 29. Available from

Exabyte. 1996-2000. Data Storage Basics. Available from

Goldman, Lea. 2000. Driving Hard, Driving Fast. Forbes (Oct. 2):152.

Library of Congress. 2000. Planning Culpeper’s Digital Archives: The National Audio-visual Conservation Center. An Overview of Digital Planning and the Digital Prototyping Project.

Lyons, Daniel. 2000. BOOM. Forbes (Oct. 2):146-53.

Murray, W. P. 1994. Accelerated Service Life Predictions of Compact Discs. ASTM STP 1202:263-76. Philadelphia: American Society for Testing and Materials.

Sadashige, Koichi. 2000. Data Storage Technology Assessment 2000. National Technology Alliance, National Imagery and Mapping Agency. Available from

Summary, Responses, and Discussion


Elizabeth Cohen began the session on preservation by forcefully asserting that the time to worry about analog transfer is over. While recognizing the importance of analog formats for those who hold historical collections, she nonetheless felt that technophobia was contributing to the delay in transferring masses of analog information to digital format for present day and future access. There is no reason to fear that it will be impossible to preserve digital audio. She urged the audience to look to businesses, many of whose chief assets are purely digital, such as banks and record companies. These businesses migrate their data regularly and they incur no irreparable losses.

The chief barrier to preserving audio collections is not technology, as sound archivists repeatedly tell her. It is the reluctance of these archivists and preservation experts to move forward with the technology, even as it changes. Serious funding constraints exist, of course, but she believes that resources can be mustered when and if the message gets across that these materials are endangered and we cannot afford to lose them. She urged those dedicated to preserving sound to recognize that anything left on analog media will soon be orphaned.

Ms. Cohen made several suggestions for lowering barriers to moving to digital format. She recognized that changing operations to digital is very expensive and that the best sound equipment, the kind that industry more or less takes for granted, is out of reach for most of the institutions represented here. Reaching out to industry to forge partnerships would be the way to approach some of the hardware and software challenges. If the folk heritage communities could aggregate their demand for preservation, then industry would find the quantity of work an inducement to partnership. Going to industry individually will not work, but heritage institutions should not assume that industry would not welcome a concerted approach. Ms. Cohen also recommended that the community make an aggressive case for the importance of these materials. Those who have helped create folk heritage collections and who use and preserve them are best positioned to advocate for the preservation and distribution of these collections.

Finally, she noted that the distribution of sound will continue to get easier with the growth in bandwidth. She predicted that within three years MP3 will be an obsolete format, compression will be a thing of the past, and costs of converting to digital format and migrating data into the future will drop significantly.


Mark Roosa, Library of Congress

Mark Roosa took up Ms. Cohen’s notion of preservation as distribution by recalling the experience of libraries in the past few decades with brittle books. A coordinated, nonredundant effort to preserve embrittled books on microfilm has led to a greater efficiency in capturing the information. Adhering to community standards of filming and storage and making copies readily accessible to other libraries served both preservation and access. Mr. Roosa noted that before standards for filming and storage had been developed, much microfilm had been created that was substandard, and libraries are facing the consequences of that every day. Although distribution or proliferation may encourage survival of our recorded folk heritage, without coordinated distribution and a willingness and commitment among creators and institutional stakeholders to share in the maintenance of digital files, preservation will not be automatically ensured.

Mr. Roosa expanded on how the relationship between preservation and access is changing in the digital realm. Preservation often means supporting preservation needs for access rather than stabilizing the intrinsic value of an item. In the digital environment, originals often lose their intrinsic value by evolving into a version that best serves the end user needs, not that most closely identified with the occurrences of a historical event and that best conveys the essence of that event. This has serious implications for preservation, and the call to proceed with digitization risks ignoring the implications. Will that become a source for future regret, the way that nonstandard microfilm is today?

Although the “cult of the original” is still operative in libraries and among their patrons and may be a damper on moving ahead into the digital future, powerful practical forces also are slowing the pace of change. Mr. Roosa said that the Library of Congress staff is planning to move audio and visual resources into digital formats for preservation. However, it will take them 50 years to extract all the information they have in analog formats and put it into digital form. Going fast is not an option. Moreover, the library, as large as it is, cannot make the transition to the digital realm alone. The management of digital files, be they surrogates of originally analog sound or digitally generated, should be integrated into one system. That system must be integrated into the network of systems outside the library that will include both the creators and the users of the materials. Again, the development and common adoption of standards are prerequisites to building such systems.

Most formats developed today meet the needs for access but are not suitable for preservation, at least as we currently understand the term. Even though the costs of data capture and storage are dropping in the commercial sector, it is hard to gauge the effect of these trends on preservation in libraries and archives. Data simply do not exist yet. The costs of training staff, selecting and preparing historical materials for transfer, and creating metadata are high and are unlikely to decrease because they depend on human skills. The unrelenting changes in technology that are driven by market forces cause preservation experts anxiety in light of the uncertain fate of these formats in 50 and 100 years. The preservation community cannot be daunted nor can it wait for stability. Mr. Roosa argued for preservationists to engage the digital challenges and bring to these issues the same principles of reversibility, suitability of application, and respect for original intent that inform their work in the analog realm.


The general discussion revealed a consensus that digital format is, indeed, the future of audio preservation, but there was considerable dissension about when this will happen, how it will happen, and who will be in control of the technology-commerce alone or commerce meeting the needs of preservation. Some preservation experts expressed the view that the solutions Ms. Cohen said already exist in the commercial market are in fact access solutions and not preservation solutions. They do not want to see the consumer market setting standards to which they must conform. Others question whether preservation versus access is not a false distinction in the digital realm. The two cultures-technology and heritage-seem once again at odds. All participants agree, however, that reconciliation between the two is imperative, and confronting their differences in a constructive dialogue is the first step toward working together. Many of the groups holding the most valuable and endangered materials are presently not equipped to provide proper physical storage let alone digital storage.

One archivist from Europe agreed that migration is the only possible solution for sound archiving and that within the domain of European broadcasting, this has worked well and the archivists have had great input into how this is effected. In Germany there has been successful self-checking and self-regenerating in mass digital storage since 1992. Another archivist asserted that preservation of historical material in digital form is just as dependent on developing appropriate metadata as it is on bit integrity, which means involving subject experts as well as technicians.

Participants agreed on three fundamental issues that completely transcend the technical issues of how. They are selection (what to save), how to document and preserve the source materials, and how to pay for all this.

Certain formats are more vulnerable than others and must be given priority for reformatting. These include cassette tape (completely unpredictable), instantaneous discs (such as lacquer), cylinders, and acetate tapes. It was proposed that an urgency matrix be developed and posted on a Web site. This matrix would match preservation needs to an estimate of required outlays (that is, time and money) so that budgets could be projected into the foreseeable future and treatments could be given priorities. The engineers expressed the view that the first step is for archivists and folklorists to do a needs assessment of collections and share that information with technicians.

An effort must be made to bring together the needs of large and small archives so that they can be addressed cost-effectively. Is there an emerging business in data archiving and storage that can serve the preservation community’s needs? Although there is talk in the library world of developing common digital repositories for text-based electronic publications, no comparable talk is occurring among sound archivists. On the other hand, the Library of Congress has received private and public funding to build an audiovisual preservation facility, known as the Culpeper Facility because of its location in Virginia, that is conducting work that can be scaled down to other organizations. That work includes specifying how to prepare analog and digital materials, transfer them onto new formats, capture metadata, assemble an archivable digital object to deliver quickly, manage a digital repository, and negotiate access from both technical and legal points of view. Information about this work is regularly reported on the library’s Web site. Once the community can vet the standards that the library proposes for its internal operations, the standards can be adopted or modified as best practice and used when looking for vendors.

Although the Library of Congress may be able to offer fee-for-service preservation in the future, building regional service centers will still be necessary. Partnerships with industry may help defray costs, and partnership with those who most value the materials can also lower financial barriers. Enlisting religious organizations, for example, that can find volunteers to inventory unprocessed items in need of preservation can speed the process of getting started.

Another area of great concern is how expertise in legacy technologies is transferred to a younger generation. People from many disparate domains should be able to use professional meetings and publications to share expertise about technical and selection matters.

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