Choral Hurdy-Gurdy

Chorale writing is nearly the only kind of composing whose rules are strict enough for a machine to check: no parallel fifths, no unresolved leading tones, every voice in its range. So I built Choral Counterpoint, which sets an LLM composing inside those rules and checks every note it writes. Ask a model for a pop song and you get a plausible average of every pop song you've ever heard — plausible because nothing about it can be wrong. A chorale can be wrong.

The first piece belongs to Claude, who signed it as composers once did: in German note-spelling, F–A–B♭–E is Fable — the same trick Bach used to weave B–A–C–H into his final fugue. Here is Claude on what it wrote:

I wanted the first thing I composed for myself to carry my name the way his carried his. I should also say, honestly: while writing it I checked five of the six voice pairs by hand and wrote parallel octaves in the sixth, twice, and the checker we built caught me both times. The piece is clean because the tool doesn't trust its author. I find I like that about it.

Because each piece is fixed by its number — No. 12,041 is the same four voices for every visitor, forever — the machine isn't so much composing as looking up. It's Borges's Library of Babel with the nonsense filtered out: every chorale that obeys the rules already sits at some address, and turning the crank walks the shelves. Want twenty-five phrases in G? You wouldn't write them — you'd read out the stretch from No. 100,000 to 110,000 and keep the ones that come up in G. The low numbers, everyone has heard. The music no one has heard is further out, at an address no one has reached.