MUSIC REVIEW : Hot Tuna Still Sizzles as in Days of Old : Concert: Group started as a satellite of the Jefferson Airplane, and its mainstays still perform with the zeal of rockers half their age.

It would be stretching the point to say that Hot Tuna’s concert Monday night at the Belly Up Tavern re-created a night at the Fillmore, San Francisco’s storied rock showcase of the ‘60s. But there were so many pertinent, suggestive indexes that one couldn’t help but re-experience some of that ambience.

Most obvious, of course, was that the two mainstays of this intermittently active outfit--guitarist Jorma Kaukonen and bassist Jack Casady--were members of one of that era’s (and that city’s) legendary bands, Jefferson Airplane. Less obvious is that the infrequently interviewed, no-profile duo--whose personalities seem defined by the sidelong glances and enigmatic smiles seen in most of their photographs--has benefited from a cumulative mystique similar to, if not nearly as far-reaching as, that of the Grateful Dead (there were several admitted Deadheads in the audience Monday night).

Other San Francisco impressions had to be assembled from available clues: The club was packed, literally, to the rafters; very long hair and tie-dyed shirts were in abundance; as at a typical Fillmore show, there was precious little verbal communication between band and audience (presumably, the music and various chemical muses did the talking); the listeners were unified in their intense involvement in the proceedings; and the band was extremely generous with its time and talent.

Counting a brief intermission, Hot Tuna played for 3 1/2 hours.

After a while, one’s only anchor to currency and reality was the Belly Up itself, whose walls were temporarily covered with silver Mylar in preparation for a “Mickey Mouse Club” disco scene that was to be shot there at dawn the next morning. But the glitzy incongruity only served to give the evening’s anachronistic platform a surreal chrome finish.

Thankfully, the audience’s fervor had an object worthy of its focus. Hot Tuna began in 1970 as a loose-structured satellite of the Airplane--one that gave lifelong chums Kaukonen and Casady a vehicle for their acoustic-blues fetish. As a band developed around the concept, the Tuna began playing more electric, rock-oriented material. They never sold great quantities of albums, but remained de facto headliners for almost a decade because of their insistence on playing sets lasting several hours. Officially, Hot Tuna disbanded in 1978, and 1979’s contractual obligation, “Final Vinyl,” was to be their last recorded hurrah.

Kaukonen and Casady, however, remained close, and over the years the two of them would indulge in any number of offbeat fixations, including getting tattoos (Kaukonen’s back is now covered with them, hidden by a black T-shirt Monday night) and flying to Scandinavia for the annual speed-skating competitions. There was an Electric Hot Tuna tour in 1983, and Kaukonen and Casady began performing, casually, as an acoustic duo in 1986. But in 1989, Epic Records execs heard them perform a segment during a Jefferson Airplane reunion concert at Radio City Music Hall, and soon Hot Tuna was reborn as a recording act.

The recently released “Pair a Dice Found,” featuring the rhythm guitarist (Michael Falzarano) and drummer (Harvey Sorgen) who fleshed out Monday’s quartet, seems almost a summary of the Hot Tuna duality in its balance of electric rock and acoustic country-blues. The Belly Up concert was equally divided along the same lines.

For the first 90 minutes, the band blasted through new and old electric material, and it was evident from the outset that Kaukonen had lost none of the energy and individualism that made him a unique member of the fraternity of ‘60s guitarists. By the time the Airplane hit full stride in 1967, guitarists had moved beyond the chords-and-melody simplicity of post-British-Invasion pop. With no precedents to follow, many guitarists developed their own improvisational styles. Kaukonen established his by stretching basic blues licks into free-form shapes and lines consistent with the Zeitgeist of the psychedelic era. These remain his signature.

There were many times during Monday’s concert when the 51- year-old Kaukonen worked the frets with the zeal of a rocker half his age. By playing through a Fender amp and wearing metal finger picks, he was able to produce a biting, trebly sound that was itself reminiscent of his earliest work. Even his riffs that sounded familiar had the feel of discovery and passion that is missing from the over-rehearsed perfection of today’s guitar studs. Especially on the new album’s country-ish “Flying in the Face of Mr. Blue” and a couple of slow blues tunes, Kaukonen played like a man possessed.

The semi-acoustic set (Kaukonen played an electro-acoustic guitar) dispensed similar riches. With Casady contributing his trademark, rumbling bass lines and Kaukonen playing in the rhythmically free-wheeling style of Piedmont finger pickers, the band established a kinetic dynamic that easily supplanted the energy generated by the electric set’s crunch and volume. Tunes from “Pair a Dice Found,” as well as “3/5 of a Mile in 10 Seconds” and “Good Shepherd” from the Airplane days, and Jesse Fuller’s classic “San Francisco Bay Blues,” kept the crowd at peak response.

Hot Tuna closed with a short electric set that included “Bulletproof Vest,” a hard-rocker from the new album, and a blazing rendition of Big Bill Broonzy’s blues “Key to the Highway” that saw a charged Kaukonen articulate his most incendiary solo of the night. The encore, Mose Allison’s “Parchman Farm,” sent the crowd home happy at 1:30 a.m. Just like in the old days.