There’s an international elite of music-theatre stars who are the Sondheim circle: people so identified with him, they seem to be not just interpreters but co-creators.

And among the most dynamic is Maria Friedman whose career took off back in the early 1990s playing Dot in Sunday In The Park With George before collecting lead roles in everything from Follies to Passion to Sweeney Todd (singing Mrs Lovett to Bryn Terfel’s Sweeney) and Merrily We Roll Along – which she’s now revisited as a stage director, picking up an Olivier Award in the process.

So when she brings her latest one-woman show to St Jude’s on Sunday, June 22, it will have authority – because the show, called Lennie & Steve, is based around the songs of Bernstein and Sondheim and although, as she tells me, she never knew the former, the latter is a close friend.

She was with him in New York just a few weeks ago and can report that, at the age of 84, he’s active, happy, working on another musical “and interested in everything: it’s an extraordinary mind that doesn’t miss a beat”.

Asked if it makes a difference to sing music by composers that you know and feel involved with, she says, yes – but in a mixed way. “It’s a thrill to have them there, on hand. But because they’re there, you want to please them and the risk is, you might not.”

The Steve and Lennie pairing, though, is natural. They make a perfect couple, having worked together in their early years as composer and librettist on West Side Story and, as independent songwriters, they share an interesting complexity, part popular and lyrical, part difficult and troubled.

“What they also share,” says Friedman, “is that they’re both quintessentially New Yorkers. They have that pulse, that edge, that take on society and they’re both men of theatre to the core, writing songs where the melody really belongs to the character who sings it, with the harmony adding a sort of psychological dimension and the words on top.

“But, of course, words are where they divide because Bernstein didn’t do them and had to hand that part of it over to someone else. Sondheim does the lot and is one of the great lyricists of all time. What he writes is clever, brilliant, funny but it also packs a punch that gets you in the stomach.”

It was the visceral, stomach-seeking trajectory of Sondheim’s work – which has never followed the standard Broadway route of neat solutions and happy endings – that first impressed her when her family took her to see A Little Night Music at the age of 14. But the family can’t have known what they were doing when they planned that theatre trip because the young Maria seemed at the time to be destined for a career in classical music – almost as a given.

Family

Her mother was a concert pianist, her father a distinguished violinist. Her brother played the violin (and still does, professionally) and Maria played the cello.

Ask her what happened to the cello and she’ll tell you it’s hanging on a wall of her home in Hackney – put there by her partner as a joke.

“I haven’t played for ages and it’s a regret that I didn’t keep it going. But it’s still in every bit of me. People tell me my approach to music is like that of a string player and it’s true: I feel like an instrumentalist when I sing.”

But just now it’s not singing that tops her agenda. She hasn’t appeared in a big West End or Broadway musical for years and says she won’t “until the right one comes along. Committing to eight shows a week for six months or more is hard work and it’s scary. So you’ve really got to want to do it.”

Meanwhile, if she isn’t actually appearing onstage, she’s still involved in making theatre happen – with incredible success. The shower of awards heaped on her 2012 production of Merrily We Roll Along, which opened at the Menier Chocolate Factory and transferred to the Harold Pinter Theatre and was the first time she’d done anything on that scale, summed it up. For myself, in all the years I’ve been a music critic with a special love for Sondheim, I have never seen a more alive, dynamic, vital or engaging show.

Directing

She talks about it in a curiously apologetic way, saying: “I wasn’t exactly up to my neck in directing experience and know that people spend years training to do this, whereas I just seemed to pop along and there it was. But I’ve spent 30 years in rooms with directors, figuring out what works and what doesn’t, and directing Merrily came very naturally to me. It was an extraordinary time I’d love to bottle and keep in terms of the concentration, the joy, the challenge of those weeks of rehearsal.”

The only surprise is that she has no big show on the cards to follow it up. But she’s reading scripts, developing ideas, and when I suggested she might think about directing Sondheim’s Passion – a piece whose UK premiere failed to hit the target and deserves reappraisal – she admitted that it’s on her mind. So maybe…

In the meantime, there’s Lennie & Steve, and I suspect it will bring the house down – if that’s the right thing to say about a show in a church.