Spontaneous Playback

Live music is quite different from the visual arts. For example, every time a musician plays a given song, it is unique, with inevitable variations from one performance to the next. As Joni Mitchell once noted, no one ever asked Van Gogh to paint The Starry Night again. But many musicians are expected to play certain songs at every concert, and these songs sound different every time. On the other hand, recorded music is more like a painting—once it's in the can, it sounds exactly the same every time it's played.

A recently announced audio format could bring recorded music closer to the live-performance experience. Dubbed MXP4, the new format is being developed by a French company called Musinaut, which rhymes with "astronaut." Like those intrepid pioneers of outer space, Musinaut is exploring the uncharted frontiers of recorded music with heretofore unheard of capabilities.

The basic idea is this: Song files saved in the MXP4 format will sound different each time they are played. For example, you might hear a different guitar solo or verse arrangement. In addition, the changes need not be entirely predictable, lending a dynamic freshness to the song each time it's heard.

The composer/performer starts by recording a song in the normal manner. During this process, they record multiple takes of the song or song sections, such as the intro, verses, choruses, bridges, solos, and ending. For example, some versions might use acoustic instruments while others are more electric, or the musical styles might be different.

Once all the versions of the song and its sections are recorded, the tracks are saved separately as WAV or AIFF files and opened in MXP4Creator, an application developed by Musinaut for Windows and Macintosh computers. The boundaries of each song section are marked, and all related sections are grouped together—for example, all the variations of each verse are grouped into a single entity. These entities are called tracks in MXP4-speak, and the different audio versions within a track are called subtracks.

Next, each subtrack is assigned a weighting factor, which determines the likelihood it will be played with the song. For example, say there are three guitar solos, and the artist wants one of them to be heard more often than the others—they might specify a weighting factor of 50 percent for that subtrack and 25 percent for each of the other two. Weighting factors can also be assigned to the order in which patterns are played, and the end can be linked back to the beginning, creating a song of indefinite length and constant variation.

Finally, the entire project is saved as an MXP4 file that can be played on a computer with the appropriate software player (see screenshot above) or streamed from a Web site using Musinaut's streaming software—check out the examples on the company's site. Each time the file is played, you hear a different version of the song. The artist can also define what Musinaut calls skins, which narrow the choices of subtracks to those that fit a particular style or mood—say, electric or acoustic—that listeners can choose according to their preference. This is a very exciting idea that brings spontaneity to recorded music, and I look forward to watching it grow.