Exclusive | Richard Simmons musical collaborator sent late fitness guru ‘something the day he passed that he never heard’

Richard Simmons was famous for revolutionizing the workout world by “Sweatin’ to the Oldies.”

And before his death on July 13 — a day after celebrating his 76th birthday — the fitness guru was toning up tunes for a musical about his legendary life with longtime Madonna collaborator Patrick Leonard.

“He had sent me some lyrics, and I wrote some melodies to them, and that was the beginning of it,” Leonard, 68, told The Post. “And then he passed … I sent him something the day he passed that he never heard.”

Before Simmons’ death, Leonard said, “I think there were eight pieces [done] … These things were very personal, and they were very autobiographical and very time-stamped, you know, at certain times in his life and his career.

“There was one about him opening his first place, his first exercise place,” he continued. “And so there’s a little storyline in there of him going to somebody else’s exercise place … and then deciding to do it himself, and then actually doing it. So you have that little triptych built in right there.”

While co-writing Madonna classics such as “Live to Tell,” “La Isla Bonita” and “Like a Prayer” — her 1989 chart-topper that is currently featured in the blockbuster “Deadpool & Wolverine” — Leonard composed the music first and then the Queen of Pop added lyrics. But he worked the other way around with Simmons, whose words didn’t always come in traditional lyric form.

“Some were more lyrical than others,” Leonard explained. “When I first started doing it, I looked at them and thought, ‘You know, let me shape these right now. I’m gonna clean them up a little bit. I’m gonna make them a little more lyric-like.’

“But I decided not to,” he added. “And so I only ever did exactly what he wrote down, which, interestingly enough, gives it a more theatrical feel.”

After Simmons’ passing, Leonard — who just released his own album, “It All Comes Down to Mood” — is not sure if the musical will ever hit the stage.

“I don’t know what’s happening with it, honestly,” he said. “I feel so bad for everyone who lost him so dramatically and so quickly … And so there’s a lot of that grieving right now. And I think once it settles, those people will come forward with whatever they think should happen, and we look at it then … I’d like to see it continue.

“But you know, part of it, for me, was talking to Richard. Because then I really have it … Without him, you know, who’s guiding it? It’s very easy to talk to him and get the feeling [for] these pieces that we wrote. And so if suddenly there’s another lyricist, or I’m writing lyrics, or a couple of us are writing lyrics, or whatever it is, it’s not his voice.”

Still, Leonard — who had never done a musical before this one — believes in the power that Simmons’ story would have on the stage.

“It’s really beautiful, because he was extremely devoted to helping people,” he said. “And there’s something about that. I think if you can tell that story right, you can move people — and even inspire people.”