Re: Issue 754: \transpose should not affect \transposition (issue 7304044)

[k-ohara5a5a]

This works, including midi and cues between transposing instruments.

I somewhat recommend doing only patch set 1 and the update to the
regtest documentation in set 3.
(Or, at least put the change in patchset 2 as a separate commit, with a
convert-ly rule to say NOTSMART on any instrumentTransposition in user
input.)

Although most people find it confusing (and would not mind changing
their scores) some people might have used the strange but consistent
logic of the behavior in master:

 clarinet = { \transposition bes \key d\major
    d'4 e' fis' g' }
 % the clarinet player is ill; give his part to the flute
 flute = \transpose d c { \clarinet }
 % ... and for some reason we need midi or cues.

If someone depended on that behavior (maybe in a more elegant or clever
way than we have foreseen) we would want to let that someone use a
version of \transposition that works as it does in current master.


https://codereview.appspot.com/7304044/diff/6001/ly/music-functions-init.ly
File ly/music-functions-init.ly (right):

https://codereview.appspot.com/7304044/diff/6001/ly/music-functions-init.ly#newcode491
ly/music-functions-init.ly:491: instrumentSwitch =
If and when you revert the negation of instrumentTransposition, you need
to get set an untransposable property on the music created here.
Otherwise, \transpose c d { ... \instrumentSwitch  ... }  has the
problem originally reported by Werner in 2004.

https://codereview.appspot.com/7304044/