Re: Issue 687 in lilypond: Enhancement: inequal MIDI quantization of equal durations (swing, rubato)

[lilypond]

Comment #10 on issue 687 by adam.spiers: Enhancement: inequal MIDI  
quantization of equal durations (swing, rubato)
http://code.google.com/p/lilypond/issues/detail?id=687

I like the misshapen cam analogy :-)  However I'm not sure it's universally  
applicable, because as observed in comment 5, there are cases where you  
want to displace the starts/ends of notes of a certain length, but not of  
another length.  For example, triplet 8th notes (or four 16th notes) would  
probably be played straight rather than swung when played over swung duplet  
8th notes.  That is a matter of taste and is impossible to predict, which  
is why I proposed a tight selection criteria for which MIDI events get  
displaced.  I thought it would be better for the user to encounter some  
displacements missing than experience unwanted ones, since it's probably  
easier to add more to the list than figure out which ones to remove.

By the way you can think of this problem as being equivalent to having two  
turntables being simultaneously driven, but only one of them has a  
misshapen cam :-)  Or even multiple turntables with differently misshapened  
cams ...

Another thing to bear in mind is that your example chooses a denominator of  
a quarter note, but this must not be hardcoded otherwise it will not cater  
for all scenarios.

I like your idea of composing the swing displacement map function with  
another global factor between 0 and 1 - this would allow users to load  
preset swing maps (e.g. Viennese waltz) and then independently tune how  
much of an effect the preset has on playback.