Re: changes.tely: deal with \transposition and instrumentTransposition changes (issue 7404046)

[Keith OHara]

On Sun, 03 Mar 2013 00:18:09 -0800, David Kastrup <address@hidden> wrote:

> "Keith OHara" <address@hidden> writes:
>
> > The \oldTransposition you suggested in
> > <https://codereview.appspot.com/7303057> has the required trickery,
> > and I just re-checked that it works fine.

> I'd prefer not giving it a name of its own, instead load a Scheme file
> on-demand that redefines \transposition ...

The backward-compatible \oldTransposition is *much* more useful if it can be 
used alongside \transposition.  If you were unfortunate enough to depend on the 
misfeature, you will probably want to change only the few instances of 
\transpose to \oldTransposition necessary to make cue notes and/or MIDI come 
out correctly under 2.17.11, and them move or adjust the \oldTranpositions to 
the correct \transposition, checking the output as you go.

> Just issue a diagnostic when seeing \transposition?

Yes, just one message per file that contains "\transposition ".  No automatic 
conversion because most uses will need no change, and we cannot tell which uses might be 
passed through a \transpose operation.

> Patterns for that will not exactly be easy to make since
> instrumentTransposition is usually an alist.

No convert-ly rule at all is the most appropriate here, because every known 
setting of instrumentTransposition /tried/ to use the /new/ behavior (and thus 
would not have worked previously).

For example in <http://www.mutopiaproject.org/cgibin/piece-info.cgi?id=119> for 
version 2.9, you find
    \tag #'horn-A {
        \key c \major
        \set Staff . instrumentTransposition = #(ly:make-pitch -1 5 0)
        \clef treble }
There are no cues, so no problems in the printed output, but the MIDI is rather 
unharmonious.