This is the most underrated Blue Note album, if not jazz album. It is an unbelievable mix between bebop and free jazz and is always hanging on the edge between the two.

And the group of musicians is fabulous -

Freddie Hubbard (trumpet)
Sam Rivers (tenor and soprano sax, flute)
Herbie Hancock (piano)
Ron Carter (bass)
Joe Chambers (drums)

It doesn't get much better than this. Check this ish out right now.