Tony Danza and singer-songwriter Josh Groban are playing an odd-couple father and son in The Good Cop, a new crime comedy premiering Friday on Netflix in which Danza's a disgraced former cop and Groban's a detective who's a paragon of virtue.

Guess who sings the theme song?

Guess again.

"I said: 'What're you talking about? We have Josh Groban — what the hell am I singing the theme song for?' " Danza, who's also a producer on the show, recalled in a phone interview earlier this month. "And so somehow, I end up singing the theme song. And it's terrific, by the way."

He sings more than once in the first season of the series from Monk creator Andy Breckman. Groban, Danza said, "accompanied me on the piano once, but I don't think he's going to sing." The lyric baritone stuck to acting, showing himself to be "determined and very earnest about his work," particularly impressing his former-boxer costar by his performance in a fight scene.

"I'm not kidding you — he did it better than the stunt man," Danza said.

Josh Groban (left) and Tony Danza in a scene from “The Good Cop,” premiering Friday, Sept. 21, on Netflix.
Michele K. Short/Netflix
Josh Groban (left) and Tony Danza in a scene from “The Good Cop,” premiering Friday, Sept. 21, on Netflix.

But then Danza, 67, knows something about exceeding expectations, having frequently done so himself, mostly through persistence and endless reinvention.

The Taxi driver and Who's the Boss? star's four-decade career includes a stint teaching 10th-grade English at Philadelphia's Northeast High School, an experience that involved a short-lived A&E "reality" show, Teach: Tony Danza, and led to a thoughtful and well-received book, I'd Like to Apologize to Every Teacher I Ever Had: My Year as a Rookie Teacher at Northeast High. He's sung and danced on Broadway, winning praise from a New York Times critic for his "breakout performance" in Honeymoon in Vegas. And he's currently touring with a four-piece band for his show Standards & Stories, which brings him to Williamsport, Pa., on Sept. 27.

He's stuck by Northeast High since his 2009 experience there, returning each spring to host a talent-show fund-raiser for the school, and said he occasionally still hears from his former students. "One of my best students, a good kid, is getting married. He wants me to come to the wedding, so I'll see what I can do," Danza said.

Tony Danza, seen here in a file photo from one of the annual talent shows he’s hosted at Northeast High School since his stint teaching there in 2009.
Michael Gray / File
Tony Danza, seen here in a file photo from one of the annual talent shows he’s hosted at Northeast High School since his stint teaching there in 2009.

On his most recent visit to the school, Danza said he was struck by what he didn't hear.

"The conventional wisdom is there's nothing good going on in public schools. And I was walking down the hallway — and Northeast's a big school —  and … you know what it sounded like? It sounded like school." He chuckled. "It was quiet."

"There's this image. We all have it, we've all absorbed it. And so when you go there, I think that you're surprised that there are thousands of miracles, happening every day in public schools all over the country. And with very limited resources. … It's a testament to the teachers, and to the staff," he said.

"Teaching's a calling. It's not a job. There's no doubt about it, because they don't pay you enough."

Danza's not done trying to add to his resumé.

"I wrote a play, and I'm trying to get it produced, here in [New York]. It's called The Characters. It's a family dramedy, comedy-drama. The big mistake I made is that I didn't write a part for myself in it," he said.

Taking a story based on "something in my family," he first took a one-day course in playwriting.

"Ten hours. No dilettante I. I started at 8 in the morning … got out at 6. I liked it, so I signed up for the 11-week course. And in the 11-week course, you get to submit [your work] and they critique you and sometimes you even act out some of the scenes from people's plays," Danza said.

"I'm actually hoping that [The Good Cop]  hits and maybe it'll help me get my play produced," he said, adding, "I think I have another one in my mind. With a part for myself."

In the meantime, he's relishing his work on the Netflix series — "It's maybe as much fun as I've had since Who's the Boss?, acting" — though he has mixed feelings about streaming TV.

"You work at it for 5½, six months, and somebody can watch it in a half a day," he said. "We live under the tyranny of convenience, and that's what this is. There was something romantic about appointment TV."

The plus side of being on Netflix? "This show, when it's released, is released in 190 countries at one time, which boggles my mind," Danza said.

"This is the 40th anniversary of Taxi this year, and I have a show coming on. I started in TV when there were three networks and the TV went off at 12 o'clock, and now I'm on a streaming service that goes to 190 countries," he said, laughing. "I don't know, it sounds pretty good to me."

Watch this

The Good Cop. Friday, Sept. 21, Netflix.