Programming computers to understand music

There's an annual competition called MIREX (Music Information Retrieval Exchange) where music transcription programs are pitted against each other to see which ones do the best job at transcribing the musical pieces note for note. Computers have great ears for music when it comes to monophonic sounds but if multiple notes are played simultaneously, as in a chord or by different instruments in a band, the software breaks. The cover story in this week's Science News is about how researchers are leveraging advances in speech recognition to develop software that can deal with polyphonic music. As these machine-learning strategies for transcription systems improve, they could even lead to "computerized-accompaniment programs" enabling a soloist and a computer to perform pieces together that are too complex for an all-human ensemble. says informatics researcher Christopher Raphael of Indiana University in Bloomington. From Science News:

Even without musical sense, Raphael's program is opening new musical possibilities. Jan Beran, a composer and statistician at the University of Constance in Germany, wrote several oboe solos with piano accompaniment especially for Raphael's system.

Raphael has performed the pieces with his system. He says that he doesn't think that those pieces could be played with a live accompanist.

The rhythmic interplays are so complex that performers can't handle them, he says. For example, one piece contains many sections where one musician plays 7 notes while the other plays 11. "Human players say, 'I'll play my 7, you play your 11, and let's shoot for where we come out together,'" Raphael says. "But the program can tell at any place in the middle of this complicated polyrhythm exactly where it needs to be."

With music this complicated, Raphael says, the software takes on a peculiar leadership role even though it does nothing but follow. "From the very first rehearsal, it understands the way the parts fit together and sort of teaches you this," he explains.

Link to Science News, Link to Christopher Raphael's site with audio examples