Association of Research Libraries (ARL®)

Sound Savings: Preserving Audio Collections

Pictorial Guide to Sound Recording Media

Sarah Stauderman
Preservation Manager
Smithsonian Institution Archives

This is a text version of a Web site created to illustrate the many prominent audio formats that may be found in libraries, archives, museums, and other collecting institutions. It is meant as a resource for conservators, curators, collections managers, and others who need to know the formats and types of audio materials in their collections. Since the first attempt to capture sound in a solid medium there has been a proliferation of media types and formats.

On the Web site it is possible to view thumbnail images of the prominent audio formats and read a short essay on the formats for the particular time period. Because preservation is an important concern, additional information about the materials that make up the formats is provided. The article that follows is an adaptation of the Web site developed in 2003 with the help of Paul Messier, Boston Art Conservation.



The first sound recordings were made with foil covered brass cylinders (1877-79, Edison) which came to be known as tinfoil records. These impermanent recordings were eventually replaced with wax- or plastic-based cylinders of varying dimensions that could be either prerecorded or recordable depending on the formulation and manufacture. The height of wax and plastic cylinders' popularity is from about 1887 (Bell-Tainter/American Graphophone Co.) to 1929 when the Edison Company discontinued its commercially recorded cylinder product. However, cylinder recorders were used to a great extent in live recording of ethnographic field notes as well as for office dictation, so archival collections may have cylinders dating from the 1930s through the early 1960s.

The length of sound recordings on cylinders depend on the dimensions of the cylinder, the numbers of grooves per inch, and the rotations per minute (rpm). Soft wax cylinders (cylinders with 100 grooves per inch) ran approximately 2 to 2.5 minutes of playing time. "Longer Play" cylinders with 200 grooves per inch ran twice as long, up to 4.5 minutes. Cylinders also have different rotations per minute, depending on the manufacturer and advances in technology, such as 120 rpm, 144 rpm, or 160 rpm.

Many manufacturers produced cylinders in their heyday, but the only substantial difference in the recording or playback of different cylinders corresponds to the diameter of the cylinder, which requires a corresponding size armature to hold it. Cylinders were recorded acoustically (also known as mechanical recording). Acoustic recording is defined as sound waves affecting a diaphragm attached to a stylus that will impress a sound track (corresponding to the sound waves) onto a recording medium.


Soft Wax Cylinders (1887): Wax cylinders were the first of the cylinders and were usually direct original recordings, though some prerecorded soft wax cylinders exist. In the first few years of their manufacture and use, they were an ivory or cream color but in later years were a medium brown color. On occasion they were used solely for dictation, and the wax could be scraped off to present a new surface for recording. Wax cylinders were made of various waxes, resins, soaps, and oils with additions of colorants, anti-fungal oils, plasticizers or lubricants, and hardeners. Wax cylinders could be solid or could have a cardboard core. Ward (A Manual of Sound Archives Administration) refers to two recipes (p. 125) for making these cylinders:

A typical recipe for the composition from which brown wax cylinder blanks were moulded was 12 lb stearic acid/1 lb caustic soda/1 lb. ceresin or paraffin wax/1 oz. aluminum oxide. Other ingredients used in Edison wax cylinders were 'burgundy pitch,' frankincense, colphony, spermaceti, and aluminum stearate.

Molded Cylinders (1902-03): Prerecorded cylinders became available, made of hardened wax or metallic soap (this also provided a sharper, superior sound). These were fragile and brittle. Cellulose nitrate cylinders with cardboard or plaster cores became available after 1908 and culminated in the "Blue Amberol" so-called indestructible cylinder in 1912.


(Diameter/length): Cylinders of different diameter cannot be played on the same cylinder machine. Here is a sampling of sizes for cylinders: 1 5/16" diameter x 4" length; 2 1/4" diameter x 8" length; 3 3/4" diameter by 6" length; 5" diameter x 4" length.


Edison Phonograph Works, London Stereoscope Co., North American Phonograph Co./Jesse Lippincott, The Columbia Phonograph Co., The American Graphophone Co./Bell-Tainter/Volta Graphophone Co., American Talking Machine Co., Pathe-Freres, and Edison-Bell Consolidated Ltd.



The grooved disc (platter, record) was an invention of Emile Berliner in 1887. Advances over the next 75 years created dozens of sizes (diameters) and colors of discs, and a variety of rotation speeds (beginning at around 70 rpm) depending on the manufacturer and materials.

Discs are made through one of two processes. In the master and mother process, a recording blank is etched to create the matrix for a permanent mold or stamping for prerecorded discs. In the instantaneous process, a stylus cuts a groove in a blank disc to capture original recordings. Discs are usually cut laterally (the groove has side-to-side impressions), though for a time in the early 20th century, they sometimes were cut vertically (so-called "hill-and-dale" impressions), depending on the manufacturer. Disc recordings span the acoustic and electric method of recording. Many discs, especially instantaneous discs, are recorded inside-out.

In general there are three eras of disc materials found in collecting institutions:

There are a variety of master recording blank materials as well as unusual discs developed for specific markets. The chronology of discs, including material characteristics, diameters, and rotations, is as follows:



Though magnetic recording proved viable and available as early as 1898 through the wire recording inventions of Poulsen, it was not until the advent of magnetic tape in the 1940s that magnetic media became popular. In part, the reason for the delay in using magnetic wire recordings was that the technology produced relatively inferior playback fidelity. Improvements in recording and playback technology coincided with the rise in the technology to produce magnetic tape.

The first magnetic tape was perfected in Germany in the 1930s and during the WWII years; Allied Forces captured samples of tapes and tape machines at the end of the war and brought them to Britain and United States for development. By the late 1940s, Ampex and EMI had developed broadcast quality audio reel-to-reel tape. The Sony Walkman (portable cassette player), introduced in 1981, made the 1980s the decade of the [compact] cassette, although the cassette had been available since the 1960s. Magnetic recording has spanned the acoustic, electronic, and digital recording age.

Formats and Tape Track Configuration:

Formats, both analog and digital, can usually be identified by the shape or size of the tape cassette or reel.

In addition to Format configurations (tapes that will only play back on the machine they were built for), there are Tape Track Configurations or Layouts. Unless a written record has been made about how the recording was made, it is difficult to distinguish the different layouts, and it is possible that important sound information can be lost in reformatting. It is essential that the playback head is the same configuration as the track to optimize playback.

Full Track: (monaural)

One track, one channel; typically on a ¼" reel-to-reel tape but can pertain to any width (special purpose ½", 1", 2"). Usually left smoothly wound "tails out" (backwards) in professional applications and environments. Note: an obsolete special purpose full track format used in TV and film applications (for synchronization) superimposed a two-track, (push-pull) 60-cycle signal across the entire width of the tape.

Half Track:

Also known as two track monaural = two tracks recorded in opposite directions, one channel each; ¼" reel-to-reel and monaural cassette

Twin Track, also known as "two-track" or "two-track stereo"

Two tracks going in the same direction, each track is a channel; typically on a ¼" reel to reel. But can also be used as a half-track mono. This also applies to ¼" in broadcast cartridges that outwardly resemble the old 8-track consumer cartridges. If "stereo" (not used as mono half-track), these are usually left smoothly wound "tails out" (backwards) in professional applications and environments. Different professional version manufacturers have/had different track widths. Note: There's a special professional two-track 1/4" format that contains "CTC": center track time code. It's a third channel containing speed & timing information for synchronization to video tape and film.

Quarter Track, also known as four-track stereo

Four tracks alternating directions: the 1st and 3rd track comprise "SIDE A" and the 2nd and 4th comprise "SIDE B." Tape stock is ¼" wide. Note: channel 1 = side A left; channel 2 = side B left; channel 3 = side A right; channel 4 = side B right.

Four Track also known as four-track quad

Four tracks, each going in the same direction, each comprising their own channel: ¼" and ½" reel to reel. These should be left smoothly wound "tails out" (backwards) as per professional applications and environments.

Stereo cassette (Phillips, aka standard format or compact cassette)

Four tracks, the 1st and 2nd track are "SIDE A"' and the 3rd and 4th track comprise "SIDE B." The standard speed is 1/78 ips but some recorders optionally recorded and played back at 3.75 for better fidelity. Tape stock is 1/8" wide. In addition to enabling or preventing recording, the tapedeck senses the presence of holes on sides of the cassette's case to properly accommodate the type of tape: "type I", "type II", or "type IV."

8-track stereo cartridge

Eight tracks, each in its own channel, going in the same direction, making 4 sides; tape stock is ¼" wide. 16 track Found on 1" and 2" reel to reel. 24 track Found on 2" reel to reel.


Wire recordings: stainless steel wire; some mid-1920s are on 6mm "wire tape."


Analog and digital tape are composed of a base, binder, and pigment. The base can be paper (c. 1946), polyvinylchloride or PVC (1946 - c.1950), cellulose acetate (1946-mid-1950s), or, most commonly, polyester (mid-1950s). PVC tapes frequently do not have a binder, but otherwise the binder is polyurethane. The pigment can be, most commonly, ferric oxide. Other pigments include chromium dioxide, metal particle, and metal evaporated tape.



Wire is stable but it is an obsolete format; its primary problems are mechanical. For instance, it easily tangles or breaks. In all studies of magnetic tape media, the least stable part is the polyurethane binder regardless of whether it is an analog or digital recording. The life expectancy of magnetic media is 10-30 years according to studies by the National Media Laboratory and the Council of Library and Information Resources.



Light (hence, "optical")—typically laser, but sometimes polarized—is used to write and read the data encoded on the recording surface of these media. In 1983 Sony introduced the Compact Disc (CD) and in 1996/97 the DVD was introduced. The magneto-optical disc (MO Disc), introduced in 1992 as the MiniDisc for audio files, is a hybrid of magnetic and optical technology is; it was intended to replace the compact cassette and supplement the CD. Instead, the technology that allows consumers to record files in MP3 data files (the personal computer, MP3 players, and the Ipod) seem to have replaced the compact cassette and MiniDisc, while CDs are slowly being replaced by DVD-R.

CDs and DVDs have several different formats (see below). The MiniDisc is one format of the magneto-optical disc technology. The MiniDisc system was introduced in the consumer audio market as a new digital audio playback and recording system. Magneto-optical disc recording technology has been used for computer data storage systems since the mid-1980s. The principal of MiniDisc is based on the Curie Temperature of magnets. In essence, at the Curie Temperature (usually, for MiniDisc, at 200 C) a magnet will lose its magnetic field and can be reoriented.

In magnetic recording systems, currents induced in magnetic heads create and read data; in magneto-optical systems, laser light writes data, and polarized light reads data from the disk because the light is reflected differently depending on the magnetization of the substrate (this is known as the Kerr effect).


Magneto-Optical Disc: Known as the "MiniDisc" for recording sound files, this is a thin (5mm) magnetic film disc, 63 mm in diameter, enclosed in a hard square case. Very high heat can eliminate the magnetic flux that encodes the information. Otherwise, there is very little information on the longevity of this medium.

CD: The CD is a laminated disc of polycarbonate plastic, a reflective metal (aluminum, gold), and lacquer. There are two physical sizes: 12 cm (4.7 inches) and 8 cm (3.1 inches), both 1.2 mm thick, made of two 0.6mm substrates glued together.

DVD: Digital Versitile Disk or Digital Video Disk has the same dimensions as a CD. A DVD is essentially two thin CDs laminated together and contains additional adhesives and temperature sensitive dyes. A DVD disc can be single-sided or double-sided. Each side can have one or two layers of data. The amount of video a disc can hold depends on how much audio accompanies it and how heavily the video and audio are compressed. There are many formats of DVD, depending on the ability of the DVD to be written once or multiple times, and whether it can be erased.

In both CDs and DVDs, damage caused to discs comes from poor storage and handling, although there may be inherent vice in the materials used to create the disc. Unfortunately, it is almost impossible to characterize the materials of these discs because manufacturers change materials frequently. As with all machine-readable formats, the ongoing development of technologies ay render a CD or DVD obsolete (unreadable) even when the medium is stable.



1. Associations

AES Audio Engineering Society

ARSC Association of Recorded Sound Collections

2. Books

Butterworth, W.E. Hi-fi: From Edison's Phonograph to Quadrophonic Sound. New York: Four Winds Press, 1977.

Byers, Fred R. Care and Handling of CDs and DVDs. Washington, DC: Council on Library and Information Resources and National Institute of Standards and Technology, 2003.

Dale, Robin, Janet Gertz, Richard Peek, and Mark Roosa. Audio Preservation: A Selective Annotated Bibliography and Brief Summary of Current Practices. Chicago: American Library Association, 1998.

McWilliams, J. The Preservation and Restoration of Sound Recordings. Nashville, TN: American Association for State and Local History, 1979.

Pickett, A.G., and M.M Lemcoe. Preservation and Storage of Sound Recordings. Washington, DC: Library of Congress, 1959.

Read, O., and W. L. Welch. From Tin Foil to Stereo: Evolution of the Phonograph. Indianapolis, Indiana: Howard W. Sams & Co. 1959.

Van Bogart, J. Magnetic Tape Storage and Handling: A Guide for Libraries and Archives. Washington, DC: National Media Laboratory and Council on Library and Information Resources, 1995.

Van Praag, P. Evolution of the Audio Recorder. Waukesha, WI: EC Designs, Inc., 1997.

Ward, A. A Manual of Sound Archive Administration. Hants, England: Gower Publishing, 1990.

3. Web Sites on History and Media Types [listed here with permission; current as of 9/2003]

The History of Recorded Sound Technology

Optical Storage Technology Association

Recording Technology History

The Edison Museum

Consumer Audio

Edison Cylinders

The Internet Museum of Flexi / Cardboard / Oddity


4. Web sites on Preservation

Library of Congress Preservation of Sound Recordings FAQ

Audio Preservation Bibliography and Web Reference

5. Vendors

The Cutting Corporation


Art Shifrin

Steve Smolian

Richard Hess


The author wishes to thank Paul Messier, Boston Art Conservation, for formatting the images and text for the Web site; Art Shifrin and Richard Hess for clarification on format types and fascinating details about them; and Sam Brylawski, Allan Goodman, and Larry Miller, Library of Congress, Motion Picture Broadcast and Recorded Sound Division, for information and allowing me to photograph their collection of formats.

This paper represents work carried out for a federal government agency and is not protected by copyright.