Can a chord contain both the C and C♯ notes? Or do you always have to use D♭ rather than C♯ in a chord that already contains the note C?
I'm guessing the answer is no, both C and C♯ should not be allowed - but I do see a lot of inconsistency on the web with what enharmonic is used to describe a chord.
For instance, take the
A♭m chord. I'm pretty sure it is correct that this chord contains the notes A♭, C♭ and E♭ ? In many places I look online, they say the C♭ is a B. But I don't think that is right, because in the A♭ major scale, the B is flat.
So therefor, going back to my question, a chord in the key of A♭ can never contain a "straight" B note. The B must always be one of B♭, B♯ or B♮. And if you're talking about a note that represents the 3rd, then that note must always start with 'C' - and therefor the minor third in Ab major can never be described as B.