Jimmy Knepper, a jazz trombonist best known for his productive but stormy association with Charles Mingus.
Over the course of a career that began when he was in his teens, Mr. Knepper was a featured soloist in countless bands, big and small. But his reputation as one of the most original trombonists of his generation rests largely on the music he made with Mingus from 1957 to 1962.
Mr. Knepper's distinctively gruff sound and loose-limbed phrasing were essential elements in some of the most celebrated albums by Mingus, the great bassist and composer, including ''The Clown,'' ''Tijuana Moods'' and ''Mingus Ah Um.''
The jazz critic Leonard Feather wrote that Mr. Knepper's ''solos with Mingus are intricate, beautifully structured and complete statements.''
But relations between the plain-spoken Mr. Knepper and the notoriously volatile Mingus were often tense, and they came to an abrupt and violent turning point during preparations for a New York concert in 1962. Mr. Knepper recalled in a 1981 interview with Lee Jeske of Down Beat magazine that in the course of an argument about Mr. Knepper's role as music copyist for the concert, Mingus ''just kind of slapped me in the mouth,'' and the blow ''just happened to break off my incisor.''
The injury seriously affected Mr. Knepper's embouchure; it took him several years to regain his full range on the trombone.
Mingus was convicted of third-degree assault (his sentence was suspended), and a fruitful collaboration was seemingly ended forever. Surprisingly, though, Mr. Knepper worked with Mingus again in the 1970's, appearing on the album ''Let My Children Hear Music'' in 1971, at a Carnegie Hall concert in 1976 and on the last three albums Mingus recorded before his death in 1979.