From the very beginning of his musical life, the Brookline-born pianist/composer Donal Fox has mixed idioms — the European classical tradition with African-American jazz. A young virtuoso, he studied classical piano and, at home, improvised with his clarinet-playing father and heard the music of classical and jazz greats side by side. At 17, he attended the BSO’s Tanglewood Music Center on a scholarship. Studying composition with the likes of Gunther Schuller and T.J. Anderson, he became an accomplished composer as well, winning residencies at Tanglewood and the St. Louis Symphony, a Guggenheim Fellowship, and a commission, Gone City, from Boston Ballet.

In the ’90s, Fox became more prominent locally as an improvising musician. He performed and recorded in duos with the likes of Oliver Lake, David Murray, and John Stubblefield. These pairings brought out all of Fox’s virtues as composer and performer: his compositional awareness of harmonic and textural shapes and possibilities, his classically infused pianist sensitivity to dynamics and to the complete range of the instrument, his virtuoso touch and marksmanship — and that allowed him to create gossamer clouds of harmonic accompaniment or fearlessly stabbed-out single-note exclamations up and down the keyboard. He was by turns lyrical and explosive.

In 2000, Fox began working with one of the most traditional of all jazz ensembles, the piano trio. Here he was able to essay his own compositions as well as use material by Thelonious Monk and J.S. Bach as taking-off points for far-ranging group improvs. If the trio has had any shortcomings, it’s that the propulsive rhythms occasionally bury his considerable range as pianist.

Now Fox is taking his small ensemble in another direction, bringing the hot-shot young vibist Stefon Harris in to join him with bassist John Lockwood and drummer Yoron Israel. The group will perform next weekend at the Regattabar and at the Labor Day weekend Tanglewood Jazz Festival.

Like Fox, Harris has a mixed background. He was trained as a classical percussionist at the Eastman School of Music and the Manhattan School of Music — and he has also recorded three highly regarded albums for the prestigious Blue Note jazz label. Fox first heard Harris at the latter’s Isabella Stewart Gardner Museum artist-in-residence concert last year. Although originally billed as a soloist, Harris had been stretching out more and more as a composer, and in interviews he’s made his compositional ambitions clear. The two talked a bit after the Gardner concert, and Fox sent Harris a copy of his Gone City (New World), a collection of Fox originals performed by the composer with various duo partners, including Lake, poet Quincy Troupe, and clarinettist Eric Thomas. It featured improvisations as well as such through-notated pieces as the concert version of the title ballet suite.

As Fox put it, " I didn’t give him just jazz; I gave him my compositional stuff. A week later we talked on the phone, and he said, ‘Man, you’ve listened to a lot of music.’ I figured, if he’s hip to that, then this is a cat I can really work with — that there were a lot of possibilities. " For his part, Harris adds in a separate conversation, " Sometimes pieces that combine both idioms will be too much jazz and not enough classical or too much classical and not enough jazz. But Donal strikes a balance, with a clear understanding of the classical tradition and a real understanding of jazz. "

For the Regattabar gig, Fox is writing new arrangements of previously performed material as well as new pieces. An obvious model from the beginning of his " Blues on Bach " programs has been John Lewis, who wrote Baroque-like themes for the Modern Jazz Quartet with Milt Jackson’s vibes in mind. " One thing I thought was missing in the trio was a more polyphonic melodic element, " Fox says. He’s also looking forward to the varied textures that a new voice will add to the pieces — for example a " highly orchestrated " passage of counterpoint between bass and vibes. " The trick is to have the arrangements but keep the freedom. I like it when people say, ‘Jesus, was the bass improvising parts to the Bach you played? That’s unbelievable!’ Because it comes out naturally. "

Fox recalls his first Monk/Bach program at the Regattabar — in the audience were Schuller, FM talk-radio host and jazzhead Christopher Lydon, and the classical pianist Veronica Jochum, who has since played his Toccata on Bach. " There were classical people digging what was happening and the jazz people were digging it. It was a nice feeling, building this bridge. That’s when I thought that those two worlds really could cohabitate, and not in the Third Stream sense, but coming out of me, because that’s where I’ve been. "

Donal Fox’s trio joined by special guest Stefon Harris plays the Regattabar next Thursday and Friday, May 29 and 30; call (617) 876-7777.