The elegant environs of Knoxville’s Bijou Theatre notwithstanding, Hot Tuna’s acoustic performance seemed more like an informal back porch gathering rather than the sedate circumstance a 110 year-old theater might otherwise imply. Of course, that’s hardly surprising. “It’s been awhile since Jack and I did our duo thing,” Jorma later noted on his blog. “But it’s like riding a bicycle.

As was apparent throughout Kaukonen and Casady’s 25 song set, it’s still a smooth ride indeed. Making a seamless segueway from one hushed offering to another, the two longtime pals and partners were so effortlessly adept and seemingly undistracted that at times they appeared they might have played the entire show in their sleep. Indeed, Casady barely looked up from his oversized bass, while Kaukonen’s easy, effortless vocals suggested at times he was singing to himself. Then again, that’s the advantage of playing as part of a union that’s lasted practically 55 years, nearly 50 of those in their own tight knit twosome. While other players have drifted in and out of Hot Tuna’s ranks over time, these days, in their current acoustic setting, it’s simply the two, a nimble duo that knows and anticipates one another’s moves and interlocks easily and without hesitation.

Casady is the quieter of the two, both in terms of his comments to the crowd (he only spoke at the concert’s conclusion, and then only briefly and seemingly in jest), as well as with his playing. Although he used his bass to provide deep fills beneath Kaukonen’s lithe fretwork, consistently set the pace, and even provided an occasional understated lead to mark a change in tone or tempo, he seems intent on maintaining a role in support, a job that he does easily and unassumingly at that.

Indeed, several times during the show, members of the audience could be heard shouting “Turn it up, Jack,” as if to encourage the reticent bassist to extend his amplification. Casady didn’t glance up, although after repeated calls from the crowd, Kaukonen turned to his partner and joked, “Did you bring the family tonight, Jack?” On several occasions the duo exchanged a few chuckles, their smiles betraying their knowing connection. Yet aside from Kaukonen’s occasional introductions, the communication with the audience was limited to the music.

As expected given their lengthy history and broad blues-based catalogue, the majority of the songs in the setlist were well known to their devotees. Dusting off several standards of their own invention or interpretation (“Candy Man,” “New Song for the Morning,” “Hesitation Blues,” “Keep Your Lamps Trimmed & Burning”), and others gleaned from an archival American songbook (“Nobody Knows When You’re Down and Out,” “Brother, Can You Spare a Dime,” “San Francisco Bay Blues”), the pair performed practically everything the audience anticipated , with the exception of “Keep On Truckin’,” a song likely best suited to their electric shows. A surprisingly loose and extended “Good Shepherd” was saved for later in the performance, while the sole encore, “Water Song,” capped the concert effectively after nearly two hours. Regardless, their inauspicious stage presence and a similarity in style that lingered from one song to another suggested an offhanded feel of familiarity allowed for an evening of decidedly low key entertainment. For many in attendance, it felt like a welcome reunion and more than a bit of nostalgia, a fact that became all the more evident at the merch stand during intermission, where classic Hot Tuna and jefferson Airplane CDs were offered for sale and in fact selling briskly.

Ultimately, the casual approach and clear compatibility that exists between these two men makes a Hot Tuna show both the unique and unassuming proposition it is. No props other than two chairs are needed, and any attempt at grandstanding or more than a perfunctory presence wouldn’t be appropriate. Even so, based on legacy alone, any performance by Hot Tuna is reason enough to be a festive occasion for the faithful.