accelerando beams

[Peter Lutek]

i need to make some "accelerando beams" - you know, the ones in modern 
notation with two beams starting close together and getting gradually 
further apart towards the end of the beamed group of notes. afaik, this 
is not currently supported in lilypond.

i'm thinking of making this by having two polyphonic eigth note lines 
with the note/stem postitions tweaked to be concurrent. then i would 
make just the notes and stems of one of those lines transparent and 
adjust the beam angle to be sufficiently different from the other one to 
produce the desired effect.

does this sound workable, or has someone already found a better way? if 
someone has already done this, i would love to see code!

many thanks!

-p