Same guy, but ten years later, he was doing his doctorate* in music, called me up and said he had another programming problem, was I interested in giving him a hand?
Heck, yeah!
To this day I still don't know what I was programming. My total knowledge of music is encapsulated in: there are 12 evenly-spaced semitones in an octave, and one of the notes is 440 Hz. I still don't understand why the notes are labelled A..G with seemingly-random sharps and flats, rather than just 12 notes A..L.
Anyway, so this was something to do with note frequency combinations (chords?) that sound good, and he had some theory about certain ratios being better than others. He showed me a couple of combinations that he'd calculated by hand; I'd do some programming; we'd mull over why it was wrong. Early next morning, we had his list, selected from some homongous search space that would have taken him decades to do by hand.
I also remember that half-way through, he wondered aloud why the ratios weren't constant, and I randomly said well, maybe it's something to do with that inner-ear spiral thing and the frequencies line up on each turn or something, like maybe that's why some people are musical and some aren't.
Another long pause, then he said "Sh*t, yeah". I don't know how far he got with that idea, but he was pretty excited at the time.
* edit: or possibly his masters, because his doctoral thesis is dated five years later (maybe it just took a while to complete)