Return to Forever had a few acoustic cuts. No Mystery had a few and the earlier ones were mostly acoustic, although Chick would break out the distorted Rhodes on them too.
Most of the acoustic "prog" that I know of is more jazz than rock though.
Early Zawinul was acoustic, but not terribly fusiony at that point yet.
You could try the Hancock/Corea dueling piano recordings "An Evening with Herbie Hancock & Chic Corea"
How about some Freddie Hubbard - "Red Clay"
Enjoy,
Bob
Most of the acoustic "prog" that I know of is more jazz than rock though.
Early Zawinul was acoustic, but not terribly fusiony at that point yet.
You could try the Hancock/Corea dueling piano recordings "An Evening with Herbie Hancock & Chic Corea"
How about some Freddie Hubbard - "Red Clay"
Enjoy,
Bob