How did you hook up with writer-director Ché Walker on Klook's Last Stand?

I was looking for some other way of making money when my twin daughters were born. It was Asher D who recommended some places to go to for acting lessons. He told me about the Identity drama school in east London and one of the first classes I did there was taken by Ché. He turned out to be a fan of my music. He was putting together a musical, Been So Long, at the Young Vic. I auditioned and got the part.

We're both similar ages and we were always having a laugh, cussing each other. I have a big respect for the man – he’s a very eloquent writer. I played a bartender in Been So Long; my part was quite minimal. Then Ché wrote me my own one-man show, Lovesong, a 45-minute monologue. That’s quite a big step to take. But how do you eat an elephant? One mouthful a time.

What was your previous experience of theatre?

I was always acting as a kid and when I went to Chetham’s [music school] at 16, they had a drama club as well as the music. I was the Pirate King in The Pirates of Penzance – I shared the lead with Max Beesley. But it was always about music for me. It's what I've done since the age of eight: orchestras, brass bands, choirs.

How does scoring a stage show differ from writing a song like There's Nothing Like This?

With my own stuff, I always start with the music, then add the lyrics – I wasn’t sure if I could do it the other way round. But it’s good to test yourself. Ché approached me about his new show, Klook's Last Stand, and asked: could I write some music? The co-composer Anoushka Lucas and I wrote our parts separately, but we also collaborated on bits and pieces. She’s a great songwriter – she knows how to tell a story.

You've worked with the likes of Angie Stone, Erykah Badu and Carleen Anderson in the past – what’s the secret to a good collaboration?

Simply put, it fuels the creative gene in me. My original thought was to work with people I really respect – the old-school masters. Since then, my career has turned into one big partnership. My feeling is always: "I hope this works." I’ve been in many situations where you’ve got together with people at long last and the vibe isn’t there. It’s all down to the vibe. With some people it works from the first go.

How did Stevie Wonder end up on your last album, The Man?

I’d been meeting Stevie for years. The first time was in 1984. He got to hear my music through my old manager Keith Harris and said he really liked my stuff and wanted to write me my first No 1. But with Stevie, you have to be patient. The man is so busy. We first got into the studio in 2000, and not just into the studio. He was in town for two weeks and we went to restaurants and clubs together too. I had time to decompress and hang out with the guy. It wasn't just: “Come into the studio now or never.”

Does Stevie know how to have a good time?

You want stories? Hmm, I can only give you a clean one. He was hungry and wanted some lunch so we phoned up a big hotel. They said: "The chef doesn’t start till five." We said: "We’ve got Stevie Wonder with us!" There was a 30-second pause before they came back on the line: "You can come down right now." When we got there, Stevie found a hair in his burger. I think someone got fired that day.

You were awarded an MBE in 2012 – how did that feel?

I got this phone call from the British Council saying they wanted to nominate me. I put it to one side. I’m not a mainstream person and an MBE? That seemed pretty mainstream to me. I was away in Italy and came back to this letter saying: "Would you like this award?" Making music all my life and getting recognition for it – it felt quite humbling. At the palace, I had the best haircut, the best suit. I took my missus and my mum and dad. The rest of the family met us outside for a photo.

Were your parents always supportive of your music?

My dad was a session drummer in the 1960s and 70s. He used to play with the Rolling Stones and tell me about jamming with Jimi Hendrix. So he totally understood the industry. But when I was offered a record deal at 16, he left it up to me. I had guys asking if I could manage a limousine picking me up every day? It sounded nice but I thought: if I don’t last, I’ll have nothing to fall back on. Some people try and get things as quickly as they can. Others have their heads on their shoulders. So I went to music school.

Does theatre find it harder to pull in young people than music?

It’s in the language, how you present things to them. Like trying to get people to go to the opera – it’s not really speaking to the everyday person. The stuff that Ché’s been producing over the years is very street and in your face.

People were crying at the end of the dress rehearsal of Klook. It moved me what I was hearing and I've worked on the thing. The performances are very straight-up, no fluff about them. And it’s not done in a musical, Liza Minnelli way. It’s a play with songs and they all fit in perfectly. You’re not thinking: "Oh my god, here comes another song." You know what I mean?

Do you think music today has enough soul?

I think there's an element of it yes. There are lots of kids who are pop stars in urban music. But there are also kids who aren’t getting the limelight but are making that neo-soul sound. They could do with getting a bit more publicity. Young artists like Ego Ella May who is doing really beautiful stuff; Shan Smile, who's a great singer and guitarist; people like Kevin Mark Trayle and Sharlene Hector. I met Lianne La Havas at a PDiddy thing – as you do. She said she was a fan. I didn’t speak to PDiddy.

What's the biggest thing drama school taught you?

That it's a bigger deal than just reading the lines. It’s all about getting into character – learning about the person you are playing. You need to know their history because you're not playing Omar; you're playing someone else.

• Kook's Last Stand runs until 6 July. Box office: 020-7870 6876. Venue: Park theatre, London, N4