Originally Posted by Rubato

But those diatonic notes have no real bearing on the tonality as they aren't structural, if you follow the bass it makes a clear step wise decent towards the sub dominant then wraps itself around the dominant before leaping back to the tonic. The diatonic chords are passing between these structural points just as much as the non diatonic ones, calling it a passing chord with no context is just bad terminology.




not necessarily no, it would have moved away from the tonal center but cannot abandon it without establishing a new center or using multiple non functioning chords, you could even write a few measures in a different region without losing the initial tonal center.