It’s 2:30 in the afternoon on Thursday, March 15, and the soulful sounds of jazz singer Patti Austin are reverberating from the empty Mizner Park Amphitheater, offering some free entertainment for strollers, diners and curious parties throughout the Park.

She’s rehearsing for her bang-up performance of Gershwin reinterpretations at Festival of the Arts Boca later that evening, but she needs little preparation. Standing onstage in casual clothes and sunglasses, her hands buried in pockets, she croons indelible tunes like “Funny Face,” “I’ll Build a Stairway to Paradise” and “Swanee” with a time-honored effortlessness, her voice sounding half as young as her 61 years.

Occasionally, she has to tell the four-man band playing behind her to slow down the tempos of the songs; if the band members had any faults, it was that they were too excited about performing these complex arrangements with a Grammy-winning interpreter of the Great American Songbook.

Indeed, Austin’s resume can be intimidating. In a career that’s spanned more than five decades, she has had enjoyed 18 charted singles and 17 studio albums, dueted with Michael Jackson, George Benson and Luther Vandross and, perhaps most impressively, dropped 140 pounds a few years back after undergoing gastric bypass surgery to combat type II diabetes.

But she remains a humble, funny personality onstage, telling her tour manager at one point, “Is there any way I can hear the band in the monitor? It would help a lot. At this point, I’m just hearing myself, which is great for me … but I need some cojones in my monitor! Or am I just deaf?”

She also showed her insight and sense of humor in short interview with me, following her afternoon rehearsal.

How long have you been performing Gershwin?

Probably my whole career. I started when I was 4. You can’t be a girl singer in America from the era I started in and not sing Gershwin. I grew up during a time when the Great American Songbook was still in the pop market.

What inspired you to release “Avant Gershwin” – to reinterpret these songs in this new, avant-garde way?

A magnificent arranger named Michael Abene, who works with WDR Symphony Orchestra in Germany. We decided we wanted to go a little crazier with Gershwin than most people do, because Gershwin can take it!

The weight you lost is really inspiring. What advice to you to for people who want to do the same?

Push away from the table and do push-ups! I had gastric bypass, but it has nothing to do with how you keep it off. You have to eat less and work out more, and as you get older, you have to eat even less and work out even more than that. You have to weigh what’s important to you. When I had my surgery at Cedar Sinai, where you had to go before the board of directors of the hospital to be approved, I said to them was that I wanted to have the surgery for the quality of my death. And they looked at me like, what do you mean? I said, “I don’t want to die a horrible death. I’d rather have a bus hit me than deal with the repercussions of 145 extra pounds on my ass all the time. I had to weigh it and finally realized that if I didn’t do something about it, it was going to kill me in a very bad way. That outweighs whatever little pork chop I can’t eat.