Until a few years ago, audio preservation and transfer involved re-recording to 1/4" open reel analog tape, mostly for the following reasons:
1. The only medium with which there was any significant history was 1/4" analog tape.
2. The 1/4" analog tape format was in widespread, commercial use since 1949, thus it was reasonably predictable that the necessary playback equipment would be available into the near future. If the equipment to play back 1/4" tape was not readily available, then it could be more easily fabricated (or restored to proper operating condition) than most other media players of comparable quality.
3. Storage media for digital audio did not have proven long term life, nor was there any certainty about which digital playback devices will be available in the future.
4. Problems in digital audio playback would often result in total failure, i.e. mutes.
5. No matter what audio restoration procedures were available, the future would bring improved techniques and equipment. [While this is still theoretically correct, the number of qualified personnel has fallen dramatically in the past few years.]
For these reasons, audio preservation consisted in the past of flat transfers to 1/4" analog magnetic tape with no processing that might interfere with future advances in audio restoration technology.
Although now out of date, the procedures for audio preservation (which was described as "archival audio re-recording") were described in the Sound Recordings Procedures Manual (right-click to download in PDF format) issued by the National Archives and Records Administration. This manual contains still excellent standards and tips for handling 1/4" tape in general. Proper leadering, labeling and handling practices for 1/4" analog tape are discussed in detail, as is the need to use slotless hub reels.
The use of 1/4" analog tape for audio preservation and transfer has all but disappeared. Analog tape is relatively expensive and in limited supply.