Of course (as we all probably know) A# and Bb, for example, are in fact two different notes, each with a slightly different pitch. They don't really meet in the middle, they were just organised into a compromise note when key and fretboards were invented. But don't let that trouble you. I don't even know the names of half the keys I play in. In DADGAD, for example I've no idea what chord I'm playing in 1st position, in either shape or pitch - put on a capo and I'd never be able to tell you. It's just sounds right for that point in the song.

Ears are always best for music. After all, that's all the audience's is allowed to use.

Tom