There's no mistaking it when Ku-umba Frank Lacy really gets going. He lifts his trombone to the sky and then plunges it back to the ground in a split second. Up and down the long horn goes while the note he's suspending spreads far and wide.

"I'm into a sort of rarefraction of the sound," says Lacy. The opposite of compression, rarefaction waves expand with time. (I looked it up.) In terms of Lacy and his trombone, "I expand the instrument in kind of an arc, going up and down and the sound spreads out."

Did I mention that Lacy's first degree was in physics?

When I suggest that this is an innovation, Lacy says, "I'd shy away from the word 'innovation.' 'Unique' would be the more logical term for it." Lacy performs Monday evening at the Bop Shop with a band whose name is also unique: 10³²K.

"It's the Planck temperature at which matter disappears — ceases to exist," says Lacy. But don't fear that you will disappear if you attend the concert. "It's an organic process with the band. We interact in a way where we have form and we don't have form."

In other words, the trio might begin with the structure of a composition by Albert Ayler or Charles Mingus, tunes featured on the group's debut album, "That Which Is Planted." "We use this as a launching point," says Lacy. "From there we go free, free-form, and free-informed."

The group's drummer, Andrew Drury, explains further: "The free area is a place to get into a kind of dream time, a zone of deep internal flow where potentially anything is possible. We are very attuned to each other. One guy makes a move and the others are right on it, offering immediate rebuttals, counteroffers, support, jokes, etc. And everyone reacts to those. Without any one person making an executive decision the music takes whatever shape it seems to want to go."

Lacy thrives on the unpredictability of free jazz. In fact, several years ago he took on the name Ku-umba, the Swahili word for "creative."

"Playing with Frank is inspiring and challenging; he's a stunningly creative guy," says bassist Kevin Ray. "When I first heard him with the Mingus Big Band in '93, I felt that this was a guy playing music the way I want to play music. He has a breadth of knowledge and an attention to detail that's just mind blowing."

Lacy grew up in Houston in a creative family. His father was a math teacher who played guitar in a style reminiscent of Charlie Christian and Wes Montgomery. In fact, "He and Wes Montgomery did some practicing together," says Lacy. "I remember one time Wes coming by the house."

His mother is a singer who had an additional talent. "She sings gospel music, but she was such a strong basketball player she would have been in the WNBA if it existed when she was young," Lacy says.

After earning a degree in physics at Texas Southern University Lacy headed for Boston's Berklee College of Music in 1979 where he encountered a "Who Will Be Who" of future stars. "A lot of us were there at the same time," says Lacy. "We didn't know we would be some of the ones who would shape jazz to come. Greg Osby, Jeff Watts, Branford Marsalis, Dave Douglas, Kevin Eubanks, Cindy Blackman, and Wallace Roney were all there."

Next stop was Rutgers University in Newark, New Jersey, where his classmates included future greats like Steve Nelson, Terence Blanchard, and Ralph Peterson. After graduating, Lacy headed to Europe, where he found an active expatriate community of jazz musicians. "People say jazz is so democratic in America but I don't know," says Lacy. "I'm reluctant to give that trophy to America until jazz musicians can tour America like they can Europe."

He lived in a variety of European cities until the Euro became the common currency and the exchange rate got high. Lacy moved back to America, where he fell in with the New York avant-garde scene, playing with Oliver Lake, Henry Threadgill, Julius Hemphill, and Lester Bowie. It was when he started playing with Bobby Watson's Horizon that he came to the attention of jazz legend Art Blakey, who asked him to join the Jazz Messengers.

Lacy served as arranger for Blakey's band in the late 1980's. But Blakey's music was straight-ahead bebop, a far cry from the avant-garde. What did Lacy's more experimental collaborators think?

"They encouraged it," says Lacy. "They thought it was a good thing that someone from their sphere had the ability to play with Art Blakey. It gave their music credibility in a certain way. I straddle both sides, avant-garde and bebop."

He has continued to crossover. In the 1990's he played on Roy Hargrove's "Habana" CD with a Cuban band. The album won a Grammy Award. And he's occasionally ventured into R&B territory, playing with artists like D'Angelo and Erykah Badu.

Lacy plays euphonium, tuba, and frumpet, a darker, flugelhorn-like variation on a trumpet. But his main instrument remains the sometimes under-appreciated trombone.

"The trombone isn't as popular an instrument as the piano, guitar, or tenor saxophone, but it's kind of a shame because some of the greatest arrangers were trombone players: Slide Hampton, JJ Johnson, Bob Brookmeyer," Lacy says. "Trombonists have a special ear for arranging music because they sit in the center of the big band."

But Lacy doesn't waste time bemoaning a lack of respect. He's had an unforgettable life because of music. And he's seen the importance of improvisation in more than music.

"Playing with Threadgill, Blakey, and Bowie, I traveled a lot of places. I went to Eastern Europe before the Berlin Wall fell. I remember going through Check Point Charlie. I was invited to come to a family's house in Romania when Ceausescu was in power. The state would cut off the electricity at a certain time of night, but with candles they were able to create a lot of light in the house."