Inside his classroom at the University of the District of Columbia, jazz professor, composer and trombonist Calvin James Jones Sr. was tough on his students. Often smiling, but always demanding.

Outside, he remained a perfectionist. His friends and colleagues recall a man whom they credited with introducing the nuances of the genre's syncopated rhythms and improvised melodies to generations of Washingtonians through his teaching and performances.

"He poured a lot of music into me -- life and music," said Allyn R. Johnson, a former student of Jones's and the university's acting director of the jazz studies program that Jones helped to create. "He was different in that way. He was in your face, very adamant about playing music, trying to pull the best music out of you."

Jones, 75, died a week ago.

At a memorial service yesterday in the university's auditorium, photographs of Jones -- mike in hand, sitting before a piano, his lips pressed to his beloved trombone -- were projected onto a wall beside his mahogany casket. The UDC Jazz Ensemble -- pianists, trombonists, percussionists, guitarists and saxophonists -- performed songs composed by Jones during a two-hour jazz jam session before his funeral service.

The photographs and music told the story of his 28-year career at the university, where his jazz studies program rivaled many in the country.

As a performer, Jones jammed with such famed entertainers as Ella Fitzgerald, Sammy Davis Jr. and B.B. King. He also performed at the Wolf Trap jazz festival and with the Smithsonian Jazz Masterworks Orchestra. And he made history: Jones was the first African American to play in the Washington Redskins Professional Band and in the National Theatre's pit orchestra.

Before joining the university, Jones taught instrumental music in D.C. public schools for more than 10 years.

Art Professor Meredith Rode described Jones as "a human force of energy, a joy."

"He was always laughing, and [was] down to earth for all his accomplishments," Rode said.

Charles J. Ogletree, a Harvard University law professor and chairman of the UDC Board of Trustees, called Jones's impact on the university "rich and unmistakable."

"His passing will leave an incredible void in our music program, but also in the lives of those he touched," Ogletree said of Jones, who recently was recognized as the 2004 faculty member of the year at the university's opening convocation.

"He introduced a form of music that folk like to say dies, but it never died," said Gail Dickson, house manager of the university's auditorium. "He kept it alive."

As Jones's family, friends and students filed into the auditorium, the lights were dimmed, and only the smooth sounds of a saxophone could be heard amid the hugs and the smiles. Later, most of the nearly 200 mourners swayed to the sounds of a saxophonist playing the blues song "In the Lion's Den," which Jones composed.

Will E. Smith, director of American University's Jazz Ensemble, remembered Jones as a pillar of the region's jazz community.

"He was a father figure to a lot of musicians here," Smith said, recalling how Jones, best known as a trombonist, once volunteered to be Smith's pianist in a pinch.

"I didn't have a pianist for a gig, and he came and played for me and did very well -- better than most pianists."

Tom Teasley, a University of the District of Columbia percussion professor who knew Jones for 11 years, took the stage in a tribute. Teasley, his eyes closed, tapped his hands on his drum, hoping to recall some of Jones's genius.

When Jones performed, "You lost the sounds of the individual instruments, and it was the combination sound that made it really wonderful," he said. "And even though the trombone sounds of Calvin will be missed, hopefully I'll be able to conjure his spirit."

Jazz musicians at UDC play in tribute to professor and trombonist Calvin J. Jones Sr., pictured right, who died a week ago at age 75.