Jay Leonhart says over the phone that he could work 365 nights a year. But he adds, just before he leaves for his daily 6 a.m.-ish run, “I just can’t do it. It wears you out. You can’t play the bass that much. Your hands need rest. If you play during the day, which I often do—commercials, people’s records, the occasional afternoon gig—and you play again at night, you can’t keep a good sense of touch.”

Nevertheless, there have been years when the sideman and front man has played 330 days and/or nights. At 60, he’s been carting his basses (he has two) around Manhattan and the world for well over 40 years and has backed Duke Ellington, Frank Sinatra, Sting, Luciano Pavarotti, Marian McPartland, Peggy Lee, Tony Bennett, Judy Garland, and Liza Minnelli. He had a 15-year association with Mel Tormé. “Barbara Carroll I’ve known for years,” he says, and adds, “There are others, like myriads of jazz people. Dizzy Gillespie I knew from working with for four decades. I played electric bass with James Brown. We’d sit and funk out.”

This month is typical for a fellow whose reputation rests not only on first-rate musicianship but also on his dry humor and easygoing manner. For the next few weeks, he’s booked into Feinstein’s at the Regency, where he’ll be playing with Feinstein himself, but he’ll leave two-plus weeks with frequent partners John Bunch and Bucky Pizzarelli? “They’ll fill in,” he says.

Increasingly, Leonhart features his songs as well as himself at gigs. (The next important Manhattan stop is the Algonquin’s Oak Room, for three weeks in July.) By now, he’s written something like 200 ditties, including those on his just-released CD, Galaxies and Planets (Sons of Sound). Generally, his tunes are a way of goofing in rhymed couplets on his life and career. Thus he offers the self-mocking “It’s Impossible to Sing and Play the Bass” and “The Couple From Duluth,” about oddball audience members. Leonhart, whose “Customs” and “Aging Planes” were the highlights of the long-running revue Secrets Every Smart Traveler Should Know, is currently penning a song about his Tormé years.

The busy guy, who left Baltimore in the late ’60s because he “wanted to play music with the big boys” and now figures he’s played with them on maybe 500 records and CDs, has his ideas about what he wants to do more of. “I want to spend time playing my own songs. I want to make a quiet little statement. We all should make a statement.”