With a musical partnership spanning more than six decades and with 163 years of life between them, Jorma Kaukonen and Jack Casady have the Hot Tuna thing down to a science. But it’s never rote. And on July 11 at a sold-out Natalie’s Grandview, the duo were in extra-fine form, perhaps owing to this being their first gig together in five months.

The pair reminisced about Jefferson Airplane opening for Dizzy Gillespie back in 1965, with Signe Anderson in the lead-female role, and marveled that while they can no longer read analog wristwatches in stage lighting and while the country debates the merits of an octogenarian president, Kaukonen, 83, and Casady, 80, are up to their jobs.

“With all there is to think about these days, it’s nice to just sit up here and wonder if your guitar’s in tune and that’s it,” Kaukonen said to Casady just before an apropos rendering of “Been So Long.”

And so it went for 100 minutes as Kaukonen chose 18 songs from a master list of many more and Casady joined in without having to be told what was coming next. That’s how close these two are – they’re almost one musician even as they head down the sonic path with vastly different gaits.

Kaukonen is the nimble fingerpicker on acoustic guitar, equally adept and low-key, slow-burning blues as he is at aggressive, my-world-is-aflame blues. On electric bass, Casady is a lead player on an instrument made for rhythm – but he never intrudes on his partner. And Casady’s partner knows when to hit the brakes and let the bassist go off on what the guitarist calls “wonderful interlude(s).”

Being apart since February obviously made for fonder hearts as the duo reunited in Ohio and opened with “Ain’t in No Hurry;” played familiar chestnuts from their repertoire including “Death Don’t Have No Mercy,” “Nobody Knows You When You’re Down and Out” and “Hesitation Blues;” offered newer, lighthearted additions such as “Where Have My Good Friends Gone;” and closed after 100 minutes with “True Religion.”

The musical closeness Hot Tuna share within the music is also evident outside of it, something easy to pick up on in a venue as intimate as Natalie’s. As the friends and colleagues continued their life-long conversation, they exchanged knowing glances, beaming smiles and inside signals known only to them but visible to all. Often lost in the music, Casady would mouth the words Kaukonen sang, move his lower body to his own low notes and throw his head back in aural ecstasy as Kaukonen riffed away in the chair beside his.

“It’s been swell, Jack,” Kaukonen said before flashing a grin so wide the stage lights glimmered off his gold tooth.