Photo: Bluesette Brothers: Toots Thielmans, the legend of the jazz harmonica, says longtime collaborator Kenny Werner constantly pushes him to explore.

You probably don''t know it, but Toots Thielemans'' sound is etched into your brain. It may have happened before you were old enough to even pronounce "chromatic harmonica," the instrument with which he recorded the opening choruses of the Sesame Street theme.

While hardly representative of a 55-year career spent creating some of the most hauntingly beautiful improvisations ever produced on this instrument, his association with the preeminent children''s program is somehow fitting.

Despite jazz credentials that include associations with masters such as Benny Goodman, Ella Fitzgerald, Dinah Washington and George Shearing, it''s easier to picture the 80-year-old Belgian-born musician on Sesame Street than on New York''s 52nd Street. It''s not just his round face and white hair, his gentle charm and his soft French accent. Nor is it his childish sobriquet (with which he was tagged as a young man on the Belgian jazz scene because his given name, Jean Baptiste, "just didn''t swing").

Mostly, it''s his emotional openness, sensitivity, and guileless nature that seem to make Thielemans so well-suited for dealing with children. These are also attributes that shape every note he plays.

Thielemans comes through Carmel on Monday, performing at the Jazz & Blues Company with his longtime collaborator Kenny Werner, a gifted pianist and keyboardist whose playing is marked by tremendous harmonic sophistication. They released a gorgeous, eponymous duo album on Verve in 2001, exploring a tremendous range of music, including standards, Werner''s originals and tunes by Herbie Hancock, Chick Corea, Bill Evans and J.S. Bach ("Sicilienne").

"Kenny likes to push me over the cliff sometimes," Thielemans says with a chuckle. "A few nights ago he went from one theme to the other without warning, changing keys, pushing me, pushing me. We played from ''Blue and Green‚'' to a Steve Swallow song, to ''Over the Rainbow‚'' back to ''Blue and Green.'' It wasn''t really a medley, it was a promenade through a beautiful garden."

If there is one thread winding through Thielemans'' promenade from the Belgian jazz scene to his debut on New York''s bebop Mecca, 52nd Street, through his days as a studio musician to his status today as a jazz patriarch, it is his emotional response to jazz. As a child, Thielemans first musical instrument was the accordion, which he played in his parents'' sidewalk cafe. Like most cultural centers in Europe, Brussels had already developed a devoted jazz following in the years between the wars.

He started playing guitar, inspired by various swing-era players, and discovered the harmonica through the popular recordings by the American master Larry Adler (who was later blacklisted for his membership in the Communist Party).

By the end of the war, Thielemans was a more than competent guitarist and his harmonica chops were coming together.

"Then a guy comes and says, ''I got some new stuff here by Charlie Parker,''" Thielemans recalls. "It was ''Two Bass Hit,'' by Dizzy Gillespie''s Big Band and then the small band on the other side with Milt Jackson. It was so clear that this was it. It was the shock wave for a whole generation around the world. It was bebop spoken here."

On a trip to New York in 1947, Thielemans had a chance to sit in at a premier bebop club in New York and the experience convinced him that he could make it in jazz with the harmonica as his main ax. Though trumpeter Howard McGhee was skeptical about letting a foreign guy with a harmonica on the bandstand, Thielemans navigated the chord changes of "I Can''t Get Started" with such aplomb, he was welcome to sit in the rest of the night.

After moving to the United States in 1951, Thielemans quickly became a busy sideman, picking up jobs with the likes of Charlie Parker.

"It''s a whole lifetime of concentration on what you''re trying to do," Thielemans says. "It''s 50 years of playing all kinds of things. That''s what you call maturity, when all of your experiences, when all your joys and pains blend together in the way you blow an instrument or the way you touch a guitar. And that''s the way I feel each time I play."