Are key signatures sharps and flats the same as passing tones?
Lets say you're playing in the key of C. No flats or sharps.
The next key up is G because, harmonically speaking, G is the closest note to C (it has the most similar tone quality ... do re mi fa so ..do and so...the fifth).
G, the key of, has an F#. Is that F# also considered a 'passing tone' in C? That is, a non-scale tone that's harmonically related as it's coming from the next key up?
Similarly would Bb (B-flat, A#) be another passing tone (or some other name for it?) as it's coming from the key of F which is the next 'lower' key from C?
And so on ... the next passing tones would be two keys away (F# and C# if you go up again to the key of D ... and B-Flat and E-flat going down).