IN ADDITION to this, different sound cards and different setting may lead to the MIDI files themselves being played very differently, which only adds to the confusion. Because of this, it always uses those extremely small MIDI files for music instead. Unlike the standalone versions, AoE Gold crams both AoE and RoR data files onto one CD, and so there is no room left on this one CD for even one CD soundtrack, let alone two of them. It is also used in the demo versions of the games. This format I believe is used in multiplayer for the players that do not have CD-s but can play multiplayer when their mates do have the CD. This format can be found as files on your computer after the install. The music is also available in MIDI format, which is a complete recomposition of the music in entirely different format that sounds completely different. In Win98 there was a nice little program CD-Player which could do it. The music data can outside the game be usually recognised by programs that are used to handle CD-audio format (your average music CD). The Audio portion of the CD is in CD audio format however and because of this you will not find this music as files on the CD with any regular Windows utilities. The CD is not Red Book format, it's Orange Book (a format which combines both Red Book which is when CD contains nothing but CD Audio, like the CD releases in the music industry, and Yellow Book which is when the CD contains nothing but data files). The original stand-alone AoE, and stand-alone RoR, on one CD each, have in addition to game data files, music in CD-audio format, which takes over half of the space on the respective CD-s.

It isn't explained in that old thread, it goes like this.

Age of empire 1 soundtrack