On Tuesday night there is a conversation at Offshore Ale in Oak Bluffs that rises above the workaday Amber-Ale-fired chatter about the big game or the latest political gaffe. Next to the bar, pianist Jeremy Berlin and guitarist Eric Johnson are carrying on what is undoubtedly the most interesting conversation of the night. Both are fluent in jazz.

piano hands
Mr. Berlin also tickles the ivories with Johnny Hoy. — Ivy Ashe

“We’re always surprising each other,” said Mr. Berlin. “At the end of the night sometimes we’ll turn to each other and say, ‘Wow, that was really cool’. You’re not even sure if people noticed it but we knew it.”

Mr. Berlin and Mr. Johnson have been playing together for 10 years. For four of them they’ve had a regular appointment at Offshore Ale, transforming the peanut-shell-dust-filled brewery to a smoke-filled Chicago speakeasy every Tuesday night.

At this week’s performance Mr. Johnson occasionally deferred, strumming his guitar percussively while Mr. Berlin took off on a flight of notes. At other times Mr. Berlin deferred to Mr. Johnson. Occasionally both spoke up, playing with equal improvisational verve and intensity, creating an odd resonance that was both separate but complementary.

Eric Johnson taught at Berklee College of music. — Ivy Ashe

“It’s a relatively unusual duo,” said Mr. Berlin between sets. “A guitar and a piano have to figure out how to get out of each other’s way and weave strands together and know when to really tighten them up and when to loosen them up. Usually these instruments serve the same function so playing together takes a certain amount of figuring out.”

The repertoire spans from tin pan alley standards to more brooding, cerebral offerings from the Bill Evans and Jim Hall catalogue, a duo that Mr. Johnson says most heavily influences his and Mr. Berlin’s style. Other influences are less immediately obvious. Mr. Johnson says he often transcribes alto sax and piano solos to reproduce on guitar.

“If you read interviews with great jazz guitar players, a lot of them imitate horn players like Lester Young or Coleman Hawkins,” he said.

jazz blackboard offshore ale
Offshore Ale is transformed from a saloon to a speakeasy Tuesday nights. — Ivy Ashe

“There’s a lot of cross-pollination,” added Mr. Berlin whose recent rediscovery of a 1970s funk album by the Meters has been informing his playing style lately.

“Jazz is more idiom then accent,” he said. “You need to know the idiom and you need to know how the phrasing works. You have to know the rules to break the rules.”

One of Mr. Berlin’s current favorite songs to play is Not Far to Fall, a composition written by one Eric Johnson.

“It’s a beautiful song,” he said. “I play it all the time by myself. I memorized it but Eric still has to read it.”

Later that evening, as they played the emotive piece, a table of heads turned up from their pizza and pitchers and paused to digest the work.

Mr. Berlin, who has been playing on the Vineyard for 30 years, splitting his time with Johnny Hoy and the Bluefish, says that serendipity played a role in his early love of jazz.

“When I grew up I just happened to fall in with people who were really into playing jazz — in equal measure jazz, basketball, beer and girls,” he said.

“Jeremy’s not as formally educated as I am and it shows how much that matters,” said Mr. Johnson, who previously taught at the Berklee College of Music. “Not at all.”

And while their music might be good for the soul it’s also good for the restaurant’s bottom line.

“They always bring in extra customers on Tuesday nights,” said Offshore bartender Erik Peckar.

The arrangement works both ways.

“Financially this is a classic Vineyard profession where you make a lot of money in the summer and its very dry in the winter,” said Mr. Johnson.

“The Offshore is so good to us,” agreed Mr. Berlin. “This is perhaps the only steady gig on the Island in the winter. For what we’re doing, it’s nice to get a gas tank and a half of money every week, but it’s really about the consistency of being able to play this music. That’s the only way you grow. The more you play the more you realize you don’t know. I go off and do my other musical things but I always come back to Eric. He goes off and does his thing but when we get together it’s a great barometer of how we’re progressing as musicians.”

Mr. Johnson and Mr. Berlin revel in promoting lesser known works and artists but jazz newbies need not be intimidated. On Tuesday as the rain beat down on a balmy December night the duo issued a musical appeal to the universe: Let it Snow.