Richard Simmons musical collaborator Patrick Leonard sent him something the day he died

Richard Simmons was well-known for his impact on the fitness world with his program “Sweatin’ to the Oldies.”

Prior to his passing on July 13, just a day after his 76th birthday, the fitness icon was collaborating with longtime Madonna partner Patrick Leonard on a musical based on his remarkable life.

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

Before Simmons’ passing, Leonard mentioned, “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,” Leonard composed the music first and then the Queen of Pop added lyrics. However, he worked in the opposite manner with Simmons, whose words didn’t always conform to traditional lyric structures.

“Some were more lyrical than others,” explained Leonard. “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 uncertain if the musical will ever make it to 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.”

Despite this, Leonard — who had no prior experience with musicals before this project — believes in the impact 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.”