I'm not so sure if I trust the exact date of the recording, but these are the From The Mars Hotel album rehearsals. The raw unrefined beauty of Unbroken Chain Alone is reason alone to listen to this set. Phil leads an acoustic version of the tune that is a must hear. Most tracks are instrumentals, but Pride of Cucamonga is one of those tunes that really shined, and could have really been something if they would have taken the time to polish it up and perform it live. An early sneak peak at Crazy Fingers is the real nugget of this recording.
As an added bonus, I'll throw in a studio rehearsal set from February 20, 1977, "The Terrapin Station Outtakes". Equinox, cut from the album, is worth a listen.
Listening for the secret searching for the sound.