i was writing chords when I came up with this progression:
IV-V-I-V/vi-IV-V-I
i understand why the V/vi-IV works--because there is only a one note difference between vi (which V/vi usually resolves to) and IV.
however, I found that replacing the V/vi with V/iii also works quite well, making the whole progression:
IV-V-I-V/iii-IV-V-I
this makes no sense to me as first of all, the chords V/iii and IV are a tritone apart from eachother, yet still work well in conjunction in this progression.
also, V/iii has very little in common with the 2 main chords that resolve to IV nicely that come to mind, V/IV and V/vi. the only similarity they have is V/iii and V/vi both have the 7th major scale degree.
voice leading withholds some explanation, but the only notes that resolve by a semitone are the root note of V/iii resolving up to the 5 of IV and the 5 of V/iii resolving down to the root of IV (see notation in C below).
this is the only plausible explanation i can find, does anyone have any other things that could explain this?