With their eighteenth album, the “rhythm and jazz” outfit the Yellowjackets (Robben Ford’s old band, for you blues fans and jazz neophytes out there) continue their journey into the calmest and yet most uncharted waters of the genre. The group actually commissioned legendary pop-artist Peter Max to create a cover painting based on this album’s rough demos. In turn, the group was inspired by that art in the process of finishing the CD. And that story serves as a perfect backdrop for an album so obtuse, lovely, and collaborative.

The sheer quietude of this material belies the complexities within-for example, the opener “Suite 15” may be the most accessible song you’ve ever heard with an unwieldy 15 beats per bar. Likewise, there’s no reason Alicia Keys fans couldn’t get busy to “March Majestic,” even as neo-gospel fans can get into the message and the backing vocals; yet Russell Ferrante’s piano is speaking chordal volumes beneath it all. From there, it gets a bit more cerebral-traditional noodly stuff like “The Hope,” the shifting emotional sands of “Free Day,” simultaneously uplifting and frightening, and the thoughtful closer “Unity.” But this band’s main attraction is the interplay between Ferrante’s keys and Bob Mintzer’s various woodwinds, one that remains as soulful as ever. This Altered State may be more mental than visceral, and smoother than ever. But mere “smooth jazz” it is not.