March 26 (Bloomberg) -- Virtuoso harmonica player Jean- Baptiste Frederic Isidor ``Toots'' Thielemans turns 85 on March 29 and continues to play, as he puts it, ``in that little space between a smile and a tear.''

The man known for the harmonica on ``Midnight Cowboy'' and the theme from the ``Sesame Street'' TV series among many others first learned to play jazz on the guitar after hearing a Duke Ellington record during the German occupation of Belgium.

His fingers no longer have the endurance to pick guitar strings for very long. These days he will not perform more than one set a night on the less physically demanding chromatic harmonica: He plans a 10-day tour of the U.S. in June.

Toots, as everyone calls him, was sitting by his swimming pool in the upscale Brussels exurb of La Hulpe on a spring-like afternoon in late winter.

Named by Quincy Jones as ``one of the greatest musicians of our time,'' Toots is now a baron in Belgium. He watched his wife Huguette gardening, with Moet and Chandon, their cute little dogs, frisking about their large lush garden.

Looking at their baronial home, I said: ``It sure is a pleasure to see someone who plays so well living so well.''

``I never did drugs,'' he explained, somewhat defensively. ``I had no expensive divorces, no children to put through college. And for 60 years I've been following my father's advice that if you make two dollars, use one to live on and put the other in the bank and forget you have it.''

Musical Tightrope

Suffering from overwork and depression, he stopped performing late last year, on doctor's orders. He is just now starting to do isolated local gigs again. ``Of course I've always been on a kind of tightrope between commercial stuff and real music,'' he said. ``Between making music for money and music that I enjoy.''

Thielemans is, however, above such discriminations. One way or another, his unshakable lyricism always finds its way directly to your heart. A partial list of the people he has soloed with illustrates his ``tightrope'' -- Benny Goodman, Paul Simon, Charlie Parker, Jaco Pastorius, Billy Joel, Bill Evans, Shirley Horn, Chet Baker, George Shearing, Ella Fitzgerald, John Scofield, Natalie Cole, Joe Lovano and Pat Metheny.

The first ``real money'' he made was when he whistled along with his guitar for an Old Spice commercial some 40 years ago. He was soon swamped by calls from advertising agencies hooked on the sound. There was another commercial coup when he played the Belgian national anthem on TV after Belgium beat Russia in soccer in 1984. ``I could have run for president,'' he said.

`Midnight Cowboy'

These days he's been working lucrative corporate affairs for the likes of Volvo AB, Ikea, and Siemens AG, mostly in Flanders. He speaks Flemish, French, English, German, and Swedish.

To please his fans in suits, he performs ``Bluesette,'' the track he wrote that has become a standard. He also plays excerpts from some of the movie soundtracks he's famous for -- ``Bagdad Cafe,'' ``The Getaway,'' ``Jean de Florette.''

Thielemans smiled that wide, life-assuring smile of his, and said: ``I don't really mind playing weddings and parties and stuff like that. Only one thing -- we try to plan it so they don't eat when I play.''

He relates to music like a child obsessed with a toy. He's even playing cops and robbers when he pretends to be worried that the ``jazz police'' are after him for the crime of commerciality.

It is lucky that Huguette is around to take care of his grown-up life. She brings him yogurt in bed at 8 a.m., after which, still in bed, he practices Charlie Parker's ``Confirmation'' in the difficult key of B Major.

Feeling Young

When we met, Toots picked up a trusty Hohner chromatic harmonica to illustrate. Hohner produces a model named for him, and one of them is never far from wherever he is.

After several false starts (``I played it better in bed''), he got it right, and said: ``It's fun to improvise in B Major. Playing music keeps you feeling young.''

There is a framed autographed photograph of that other harmonica virtuoso Stevie Wonder in his downstairs washroom. Wonder came to sit in during his 80th birthday celebration at the Blue Note club in New York. There was a big tribute concert in Town Hall last year. The Thielemans own an apartment on the upper east side of Manhattan.

King and Baron

But he feels ``very Belgian.'' With his well-developed sense of irony, he calls himself ``The Belgian King of Bebop.''

The real Belgian King Albert gave him a ring when he made him a baron on the occasion of his 80th birthday. Toots has recently lost some weight, and his finger is too skinny to wear it now.

Toots displayed the luxurious, leather-bound baronial proclamation, on which is printed, in a Gothic font, his credo, ``be yourself, no more no less.'' He explained: ``Comes from Seneca, one of those dudes.''

Toots added: ``Belgium is like a friendly old sweater that you keep wearing even though it's worn out. I still love to wear it. It reminds me of 'Sophisticated Lady,' and those other old standards you never get tired of revisiting.''