Support for "unkeyed" (but not unpitched) instruments, needed for timpani and historic brass
See https://musescore.org/en/node/154611#comment-629151. Some instruments are normally written without key signatures, even in a score among others that do use them.
I have caught myself forgetting to add the Open/Atonal key signature specifically to the timpani staff at every key change. This should be just a property of the instrument.
Comments
It should be an option on every instrument with a clef since classical scores do this with horns and trumpets (and coronets...) also.
Cornet :-)
Sometimes Clarinets do too
From what I know, most modern F horn players prefer no key signatures, as well as trumpet players. Maybe have one with key and one without key?
Hmm, I guess maybe if you limit consideration to professional orchestra players who specialize in 17th-18th century repetoire, but I doubt that constitutes most trumpet players in general.
Anyhow, the proposal is to make this a staff property, so yes, both other options would exist. The default should be to use key signatures, but those who prefer the historical method could simply set the option. It's conceivable an additional instrument with this set by default could be made available as well.