In the first Bb Blues in Mimi Fox's, "Jazz Anatomy", she plays a V min (F min7) instead of V7 (F7) in bar 4.
I usually recognize basic chord subs quickly, but this one seems to have me stumped. It could be very simple and matter of fact--"Sometimes you just substitute min7 for dom7", I guess, but I'd like to pin it down theoretically. I've flipped through one of my jazz blues comping books, and I don't see a Vmin7 sub mentioned in a list of common progressions.
I wondered if it was a temporary modulation, since Fmin7 is the ii chord of Eb maj. It's common to approach a V chord from its ii chord, and it's also common in blues to temporarily treat one of the other 7th chords as a "I" and put its ii in front of it. (so Fmin7 could go to Eb7). But that's not what happens here. F min 7 goes to Bb7.
I feel like I'm missing something very simple, so if someone could clue me in, that'd be great.
Oh...and one gripe. Why didn't TrueFire put the chord type(s) above each measure to make the progression easier to follow in the PDF? There's just tab and notation, but no chord chart.