Re: Lilypond's internal pitch representation and microtonal notation

[Wols Lists]

 On 20/09/10 14:41, Hans Aberg wrote:
>> As a related issue, have you considered how (different kinds of)
>> transposition would be handled in your pitch scheme?
>
>
> This is much simpler: the linear combinations are vectors that you
> just add. For example, if a, b, c, ... are represented by 0, M, m+M,
> ..., and you want to transpose from b to c, just add m. A sharp is M-m
> and a flat m-M. If you want transpose from a note x to a note y, just
> add y - x.
What you've missed (and I need to address) is "what is x?".

Let's say I want to transpose up three semitones. That's probably easy,
it's a minor third, but it could be an augmented second. So, trying to
remember the pitch class, is it (0,2,sharp) or (0,3,flat)? And, for your
example of that, I've currently got a modified chord engraver on the
frogs list that's added a guitar capo property. All the engraver is told
is how many semitones to transpose, and it's got to sort out all the keys!

Cheers,
Wol