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

[David Kastrup]

"Keith OHara" <address@hidden> writes:

> On Wed, 27 Feb 2013 00:47:21 -0800, <address@hidden> wrote:
>
>> On 2013/02/27 07:40:59, Keith wrote:
>>
>>> Oops.  It was \oldTransposition  but it was not put into LilyPond.
>>
>> Since the sign of instrumentTransposition has been inverted, it would
>> require serious trickery or a separate music event type to implement
>> \oldTransposition with the previous semantics.
>
> The \oldTransposition you suggested in
> <https://codereview.appspot.com/7303057> has the required trickery,
> and I just re-checked that it works fine.

Would you believe that I had already forgotten about this contraption?
It did not exactly get a favorable review from you, either.

Ok, but we'd still need to figure out how to deal with this abomination.
I'd prefer not giving it a name of its own, instead load a Scheme file
on-demand that redefines \transposition (of course, that does not work
using the given definition with #{ \transposition ... #} inside but that
is easily fixed).  That way, our proper code base steers clear of this
kind of cruft.

The question is what convert-ly should try doing about it.  Just issue a
diagnostic when seeing \transposition?  Load the compatibility file
unconditionally?  Load/warn only given certain patterns?

> Probably no-one has used \addInstrumentDefinition for transposition,
> but if someone has, the instrumentTransposition assignments already
> use ly:make-pitch, so inserting ly:pitch-negate is not too much work.

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

-- 
David Kastrup