In 2004, traders begun a massive coordinated effort to preserve the music in as good quality as possible for current and future live concert enthusiasts. Traders have scoured the world to track down the lowest possible generation of each source of each show. (Sometimes it has proved to be impossible to get in touch with the person who owns the master tape, so traders look for the next best thing - a first generation copy.) This lowest known generation is then transferred to FLAC. Currently, most audio trading takes place on this format.
Many shows were recorded by audience members to analog cassette. This master tape is known as the 'analog master', or ANA(M) in traders' shorthand notation.
The taper would then trade out copies of his master cassette: a direct copy of the master tape is known as a 1st generation cassette, ANA(1) in shorthand. A copy of the 1st generation copy is an ANA(2), etc. Generally speaking, the higher the generation copy, the worse the sound quality, since copying cassettes is an imperfect process and adds tape hiss and distortion to the sound.
Recordings can also be taped onto Digital Audio Cassette (DAT), an obscure format used by industry professionals. A master tape in this case would be listed as a DAT(M) in traders' shorthand. The advantage of DATs is that they can be cloned digitally, i.e. copied without any quality loss (unlike audio cassettes). However, it is important to keep track of digital generations as well (in case of problems or faulty copying somewhere along the chain), so a DAT copy of a DAT copy of a DAT master, for example, would be a DAT(2).
Analog cassettes were often transferred to DAT so that they could be copied without further quality loss, for example, a DAT transfer of a second generation analog cassette would be listed as: ANA(2)>DAT(1).
It is far from simple to determine what actually is the 'best' available source, as we shall explain. There are six crucial factors: