An examination is conducted of the life, career and musical styles of Richmond Matteson, an influential jazz euphonium and tuba performer of the twentieth century. The study includes a brief history of the euphonium's role in concert bands. A description of Matteson's background as a musician and clinician including education, influences and career changes will also be discussed. Analysis of Matteson's improvisational style and a transcription from the recording Dan's Blues is included. A formal analysis of Claude T. Smith's Variations for Baritone is provided, as well as a brief biography of the composer. Matteson's stylistic traits which Smith employed for the composition of Variations for Baritone are illustrated. The conclusion calls for further study of jazz styles by euphoniumists with more frequent performances of Variations for Baritone. Appendices include lists of Matteson's compositions and arrangements, a selected discography and a list of clinics and performances from 1982-1992.