IT was British violinist Nigel Kennedy who came to the rescue that summer 15 years ago. ''You can rent my flat in Hampstead,'' the enfant terrible said magnanimously. ''A funny, eccentric little place,'' Yo-Yo Ma recalls. Still, he was grateful. The rent was modest and he was practically broke. Best, he had his privacy. As the mercury rose and the flat started to resemble a furnace, Ma did the sensible thing. Then onemortifying day he was caught out. ''I was practising in my underwear, when suddenly a young couple walked in. 'Who are you?' I said, covering myself with my cello. 'We've rented this flat. Who are you?' said the girl. ''It could have been a disastrous situation, but they were also musicians and thought the whole thing was hysterical. We became instant friends and have stayed that way.'' The startled woman who saw Ma stripped for action eventually became more than a friend. Five years ago, Lancashire-born Kathryn Stott became his accompanist, forging one of the classical music world's most brilliant partnerships. Next Wednesday and Thursday at the Cultural Centre Concert Hall, they will be creating their special magic courtesy of the Alcatel Alsthom Series. A rich programme is in store - Bernstein, Beethoven, Falla and more - and while most eyes are bound to be fixed on Ma, he makes it clear that upstaging is not on. ''I have such respect for Kathy. If I ever treated her badly, she would kick me in the shins. I wouldn't dare anyway. She's a heroine in England, a big star in her own right. When we look at a score, our aim is to achieve balance. I have never thought: whatever happens, I'm going to be louder. We make music together.'' Three years his junior, Stott secured her stature as a soloist in 1978 when she became the first British woman to triumph at the Leeds International Piano Competition. That she is content to allow Ma the limelight is a measure of their rapport. Meet the cellist away from the stage and you understand something of the chemistry. ''You've waited all this time? Don't go away, I'll be right back. Order yourself some coffee, food, anything. I'll be right back,'' a hotly pursued Ma said during a recent whirlwind visit to Hong Kong which brought yet another accolade - an honorary degree from the Chinese University. After an hour's wait, what was another 20 minutes? The six-time Grammy Award winner hailed by Isaac Stern as one of the greatest instrumentalists alive had agreed to an interview. Patience was a small price. He has cropped his luxuriant thatch of hair and the slightly punk look suits him. Otherwise, nothing has changed: still the same effervescent Ma, antithesis of every off-putting thing you have ever read about superstars. ''My name? Just you try and live with it. I've lost count of times telephone operators have said 'This is no time for joking' and hung up on me when I've said, 'It's Yo-Yo'. Yo Mama, that's me.'' His Chinese parents saddled him with the catchy name when he was born in Paris in 1955. Both musicians, they also nurtured the precocious talent which propelled him on to a public stage at the age of five, and had critics comparing him with Rostropovich and Casals by the time he was 19, which has kept him at the top ever since. The rewards have been fantastic. At 38, Ma ranks among the 20th century's greatest cellists and commands an immense following. Greatness has consistently attracted the greats. Stern adores him as a music partner. Ditto Emanuel Ax, Jaime Laredo, Cho-liangLin and many more. That he manages to fit in ensemble playing when he already has a surfeit of orchestral and recording engagements says a lot about Ma's dedication. Equally admirable is the enormous amount of time he willingly devotes to teaching. Most summers, Ma can be found coaching students at the Tanglewood Music Centre, Massachusetts, and he is in enormous demand for masters classes wherever he travels. He is acutely aware of the dangers which befall the workaholic. ''Increasingly, I've tried not to take on too many things, and achieve a more delicate balance in my life. I have so few days at home in Boston, I jealously guard every minute of them.'' They are shared with his American teacher wife Jill and their children Nicholas, 10 and Emily, eight. They are a close family and nothing is more important to Ma than his marriage, though his parents were bitterly opposed to it. ''I don't know what it is that makes people that way. Some tribal instinct, I suppose, though that doesn't make it any easier to cope with,'' said the cellist, recalling the ugly scenes which erupted when he announced that no, his intended was not Chinese. ''The way the world is changing may make it easier for mixed marriages. I hope so. There's not much I complain about, but people being racist is one of them. I think Jill is the only person who knows me through and through, with all my shenanigans. ''I've known her since I was 16 years old. We met at a festival in Venice and it was one of those instant things which worked. We've stayed together ever since and I don't know anyone so good, strong and independent as my wife. I think I'd be dead if I hadn't met her.'' He says that with a grin. No real danger, it implies. Those who know his background, would agree. His years at Harvard gave him an intellectual depth shared by few professional musicians. There, in addition to music, he studied history, literature and anthropology - and that was after being at Juilliard. ''I think I developed a broader view [at Harvard] . . . I would now feel very much at ease if I had to stop playing, that it is possible to do other things,'' he told Mary Blume of the International Herald Tribune in 1989. Fours years on, he's still toying with the possibilities. ''I been playing for 33 years now. Amazing, huh? Often I wonder what I'm going to do when I grow up. What's great about music is that it enables you to record life. You are witness to unbelievablesituations and places, experiences and sorrows, and somehow you put it through this sieve. ''To me, music is not simply a career. It is the accompaniment to my life, and that's something you can live with.''