Stephen Paulus tiptoed around sheafs of paper piled on the floor of his Summit Avenue home studio, searching for a certain musical manuscript.

"I don't like stacks on the floor, but I've got so many things going this year that I need to keep track of them," said the composer. "I let myself get overbooked."

Paulus finally located the working score of "TimePiece," the first collaboration between him and his son, jazz trumpeter Greg Paulus.

Osmo Vänskä and the Minnesota Orchestra will open their season next weekend with a program that includes the composition's premiere, as Greg Paulus and other jazz musicians mix genres and performance styles.

"I should have put some sandals on," said the barefoot Paulus when he was told to sit for a photo with Greg. "I look like a hillbilly."

If so, he is a hillbilly with a national reputation. He co-founded the American Composers Forum, runs a nationwide music publishing business from his St. Paul home and has served as composer-in-residence at the Minnesota Orchestra, as well as Atlanta, Tucson and Annapolis, Md.

"Stephen always knows, on a very practical level, how to write for the instruments," Vänskä said. "I have seen scores by some composers where everything is impractical. Stephen knows how to get the best results for his ideas."

For "TimePiece" he and Greg, who has become an internationally known jazz trumpeter, brought together electronic music, sound looping, jazz improvisation and classical techniques in a 32-minute piece. It diverges radically from Stephen's last premiere performed by the Minnesota Orchestra in 2005 -- the Holocaust oratorio "To Be Certain of the Dawn."

The opening movement, "Rain (all day)," begins with recorded sounds of cars, rain and wind. A series of chords, played on electronic organ through a computer, repeats itself until the orchestra enters and overwhelms the electronics. In the fourth movement, "A Night in Tunisia," electronic sound mixes with the orchestra "playing against itself in sections by way of digital delay, managed by Greg," according to early program notes.

Maiden voyage

Stephen and Greg talked years ago about merging their classical and jazz instincts in a single piece. Stephen suggested it to Vänskä, who eagerly rose to the bait.

They describe their collaboration as "an organic process": It's as if someone brought a bowl of fruit punch to a social event, then someone added rum to the punch, which made it a little better, then someone dropped in blueberries, which made it even tastier.

Stephen went to the piano to illustrate. He played a three-chord progression that was scratched on a piece of paper, and then played it again, adding density with sevenths and ninths and then finally put minor triads atop the chords to fill the phrase with dissonance.

"This is the best part of the whole piece," Greg said approvingly. "We need to hear that over and over again."

"You like that, huh?" Stephen answered. "It's the perfect jazz, R&B chords, but we're expanding them in a sophisticated way."

Greg's globe-trotting offered challenges to their writing process. The two Skyped while he was in Tunis, Berlin and London. They kept busy through e-mail while Greg was at home in his Brooklyn loft.

"A lot of the things were interpretations of ideas I had previously," Greg said. "At the end of the day, he [Stephen] is the one who writes it on paper. He's much quicker than I am."

Childhood well spent

The senior Paulus readily agrees when it's suggested that in concept, "TimePiece" does not sound like a Stephen Paulus composition. He credits that to the sounds his son pounded into the old man's head for 15 years.

"From the time Greg was 12, 13, I've heard him play a gazillion of the jazz standards, a gazillion times," he said. "There is a sonic memory that I absorbed through the pores."

When he was in elementary school, Greg did not see a music career in his future. He was into skateboarding and extreme sports and listened to hip-hop.

In junior high, a teacher told Greg he had a good ear -- which he exercised by picking out the jazz source material in many of his favorite hip-hop samples. The quest to reproduce those sounds motivated him to practice his trumpet, often long after midnight with a friend on piano.

Stephen recalled one hot evening when a policeman, acting on a neighbor's complaint, shone a flashlight beam into the porch and asked Stephen "if we were having a kegger." Father pointed to his trumpet-playing son, who offered a few licks.

"He's pretty good," the cop said. "But it's after midnight, so keep it down."

Dad's advice

Stephen tried to discourage his son from seeking a career in music, "where your payment is often a meal after a performance," he said.

A typical teenager, Greg didn't listen. After a Stanford jazz residency, classes at Manhattan School of Music and an immersion in the New York club scene, Greg's work is now recognized worldwide.

Father and son seem eager to do this again, though Greg notes, "We'll have to see how this comes off."

He's a bit anxious to see how rehearsals with the orchestra go this week -- getting 90 musicians and a conductor in sync to a beat laid down by a jazz drummer. Improvisation has not been the orchestra's claim to fame. Stephen readily admits the gamble, but he's confident.

"If you're good and have integrity, you are always trying to do something that you're not sure will work," Stephen said. "The only thing Osmo said to me was, 'Don't make us a backup band.'"

Vänskä recalled the conversation and said he feels that Team Paulus has accomplished his wishes.

"I have seen sometimes that the orchestra is sitting there but doesn't know what to do," the conductor said. "This really makes sense and looks very promising. It's a piece written for the orchestra and for the solo group, in that order."

Stephen Paulus smiled at the thought.

"They will have plenty to do."