Hi
I can't help thinking that this has probably been suggested before, but in case it hasn't I've set out my thoughts here. In the past I've used Sibelius and I like the way that it applies sharps and flats from the key signature automatically. This really doesn't seem to conform to the way Lilypond does things, but my suggested change, I think, should do much the same. I habitually use English as the Lilypond \language, so please bear with me.
If I'm writing music in F, then I suggest that I be able to use bF as a pitch instead of bf. The F would indicate that all subsequent bs would be flattened until one is encountered with a different accidental or until the end of the current music _expression_. It should have the same scope as \stemUp or similar.
As I see it, the changes in the parser would be small: we would need to introduce an explicit 'natural' indication and to recognize capitalized accidentals. (In the case of accidentals with more than one letter, then I leave it to the implementors to decide whether all need to be capitalized or just one.)
You will notice that although the key signature will be the most probable reason for using this idea, I'm simply suggesting an extension to the way of expressing which pitches I want in a way which is independent of key signature and in keeping with the way Lilypond does this (at least the way I use it 🙂 ) It also means that all current scores continue to work without modifications.
Paul McKay