MIDI output: Possible to change PPQ?

[James Harkins]

I was just searching, without success, for a way to change the number of 
pulses-per-quarter in MIDI output. The default, 384, handles double 
divisions and triplets, but quintuplets are inexact. I would rather use 480 
for this particular file.

The section in the notation reference on the \midi mentions that it may 
include a \tempo statement, and \context blocks. Web searching wasn't 
helpful either, so I suppose I'm stuck with 384.

How hard would it be to add something like \midipulses 4 = 480? (Is it 
something I could figure out by poking around in the source code?)

hjh