He was known for his emotionally charged performances and several stylistic shifts throughout his career, and was described by critic Scott Yanow as having "attained his goal of becoming the world's greatest altoist" at the time of his death in 1982.

At the age of 17, he began playing professionally with Benny Carter and then became part of the Stan Kenton orchestra, touring with that band until he was drafted in 1943.

Along with Chet Baker, Gerry Mulligan, and Shelly Manne, and perhaps due more to geography than playing style, Pepper is often associated with the musical movement known as West Coast jazz, as contrasted with the East Coast (or "hot") jazz of Charlie Parker, Dizzy Gillespie and Miles Davis.

His career was repeatedly interrupted by several prison stints stemming from his addiction to heroin,[4] but Pepper managed to have several productive "comebacks".

Remarkably, his substance abuse and legal travails did not affect the quality of his recordings, which maintained a high level of musicianship throughout his career until his death in 1982.

His autobiography,[6] Straight Life (1980, co-written with his third wife Laurie Pepper), discusses the jazz music world, as well as drug and criminal subcultures of mid-20th century California.