Michael Feinstein and Marvin Hamlisch play Tilles

Marvin Hamlisch and Michael Feinstein bill themselves as "Two Gentlemen of Broadway" for Saturday night's two-for-one concert at Tilles Center. Or they might be called the Odd Couple.

Feinstein, fastidious and admittedly obsessive about his repertoire - the Great American Songbook, the subject of a three-part PBS documentary that concluded this week - is the go-to guy for music of the 1930s and '40s. Hamlisch, who can wow you with his facility for making up songs on the spot, has created his own songbook, beginning with hit Broadway musicals of the 1970s.

They've gotten together for only a handful of mashups before. They both say you never know what they might play. But we're taking bets you'll hear something from the Gershwins - Ira Gershwin was one of Feinstein's mentors (Rosemary Clooney the other) - and something from "A Chorus Line," the groundbreaking musical that made Hamlisch's career.

We chatted with each by phone on the road - Feinstein in St. Louis, Hamlisch in Pittsburgh.

TO FEINSTEIN: Your specialty - one could say obsession - is with the Great American Songbook. What brought a kid of 5 or 6 to the music of the '30s and '40s?

The music chose me. I had an emotional reaction. It affected me in a way that other music did not. Pop songs were so simplistically constructed, they bored me and actually made me feel uncomfortable.

How do you balance a program of Michael and Marvin?

Marvin is a marvelous pianist. One of his first jobs was musical apprentice on "Funny Girl," with Jule Styne. So he's particularly adept at playing standards. We do solo segments and dual pianos at the end. The spontaneity of it works like gangbusters. And I like singing his songs. 

TO HAMLISCH: So I understand you guys don't go with a set playlist for your concerts together. How does that work?

We kind of almost have a playlist. I do certain songs of my own or I'll play for Michael when he's singing one of mine. We sort of decide when we get together a couple of hours before the show. You could never do that with an orchestra. No one does the standards like Michael. He's the only person I know who cares so much about this music. He's devoted to it.

What's up for you next?

My big project is a new musical starring Tyne Daly. "Queen of the Stardust Ball." We're doing a reading in November. And we're hoping it takes off from there.

WHAT: Marvin Hamlisch and Michael Feinstein in concert

WHEN | WHERE: Saturday night at 8 at Tilles Center, C.W. Post Campus of Long Island University, Brookville

INFO: $52 to $102; tillescenter.org, 516-299-3100