The keyboardist on this rehearsal recording is Tom Constanten. He is playing Ron's Vox organ. Ron is absent from this session. There is no electric piano on this recording. Mickey plays glockenspiel behind Jerry's lead vocals in the bridge on "St. Stephen" as one would expect him to do.
Tom was classically trained both as a pianist and as a composer, but throughout his time with the Grateful Dead, his phrasing was stiff, staccato, and unsuccessfully syncopated. A classic example is Tom's delayed, out-of-phase right-hand harpsichordal line behind Jerry's singing "Twenty degrees of solitude/Twenty degrees in all" during "Mountains of the Moon" from Playboy After Dark, Hollywood, CA, 7/10/69. Fine counterpoint melodically, harmonically, and stylistically, but poor counterpoint rhythmically. Tom starts his phrases late and stumbles in his articulation. The halving (at times, almost a "three-quartering") of bar lines and the pretermission of phrases that mar Tom's playing at this rehearsal are characteristic shortcomings that mark his style, for better or worse. I heard Tom play live at the Psychedelic Shop on Market Street in San Francisco around the time of the release of his album Fresh Tracks in Real Time, and his playing had not changed in this regard. After the gig, I spoke with him about his music and his time with the Grateful Dead, including the challenges of playing in the band. He was candid about the joy he had felt while playing live with the band despite his inability to swing with them as both he and they longed for him to do. He spoke of his frustration at not having been able to get the hang of playing syncopated rhythms despite his intellectual understanding of them. (He is a kindly, honest, witty, and amazingly intelligent man -- like Phil, Jerry, and Robert, possessed of a photographic memory for music, literature, and history -- but he couldn't swing from a rope.) He freely admitted that his and the band's frustration with his live playing, including mutual dissatisfaction with his rhythmic stiffness and his difficulty in interpolating robust and substantive lead lines into the improvisational matrix, led to his amicable departure. He also stated that he loved and even admired Ron's keyboard attack, full, fluid, and surprisingly sprightly as it could be, and that he reveled in prepared piano and in other departures from straight-ahead playing because they freed him from the limitations of his stodgy and somewhat limited keyboard technique. In other words, he preferred to make music as he heard it in his mind, not as it was delimited by his fingers. Nonetheless, he always greatly enjoyed playing pop, rock, and blues tunes, so he decided to keep one foot in the camp of the frighteningly abstract and the other in the camp of the painfully concrete. He mentioned that it was easier for him to play the keyboard as a soloist rather than as an accompanist because of his particular and somewhat elastic sense of time. As a rendition of "Clementine" was recorded at Pacific Recording in San Mateo on 5 Nov. 1968, right after the main run of "Mickey and the Hartbeats" shows during Oct. '68, it is possible that this rehearsal is coeval with that date and may have occurred there. I believe Tom's first gig with the band was on 24 Nov. 1968; he and Ron both played keyboards the next night in Cincinnati. It is of course also possible that this rehearsal took place in Dec. '68 at Pacific Recording or elsewhere. (There was also a rehearsal featuring "The Eleven" from Avalon Ballroom on 23 Jan. 1969.) Alembic's own "long history" by Susan Wickersham (née Susan Frates) states that she and Ron Wickersham met in 1968 at Pacific Recording, where Ron was designing the first multi-track mixing console for use with the studio's new, state-of-the-art Ampex MM-1000 16-track reel-to-reel recorder. Ron and Susan left Pacific Recording in 1969 to form Alembic. (It is not clear from the history when this move took place; it may have happened as late as June or July '69.) As the Grateful Dead had their office and rehearsal space in Novato, that's where Alembic set up shop; Alembic "had its offices in the building with the Dead and separate workshop and living space behind the warehouse." That year, Pacific Recording went out of business, and Alembic acquired the 16-track Ampex recorder. Subsequently, Alembic moved in Feb. '70 to 320 Judah Street in San Francisco, and then relocated in 1971 to 60 Brady Street, taking over the former Pacific High Recording studio. (Note the distinction, which others have pointed out, between "Pacific Recording" and "Pacific High Recording.") If this rehearsal was held and recorded in Nov. or Dec. '68, Pacific Recording in San Mateo would be a likely venue. If it was held and recorded in early '69 (not likely, but possible), Avalon Ballroom 1/23/69 or Novato would be possible venues.