Rex Richardson maintains a busy performance schedule even between Rhythm&Brass tours, as a soloist in jazz, orchestral and recital contexts. He has won attention in the international jazz arena with appearances in the U.S., Canada, and Japan as a sideman of the great Joe Henderson, and has also worked with such jazz artists as Carl Fontana, Kurt Elling, and Benny Carter. He has performed as a member and as a soloist with the elite, internationally- assembled Brass Band of Battle Creek and the newly-formed BrassUnlimited, an English-style brass band featuring outstanding soloists and orchestral musicians from the U.S. and Europe.

Since his teenage years Rex has been engaged for especially difficult works such as Bach's Brandenburg Concerto no. 2 and various contemporary works. Hearing Rex in concert in 1998, Pulitzer Prize-winning composer Karel Husa was moved to ask him if he could send the trumpeter his exceptionally difficult concerto for trumpet and wind orchestra, explaining that he had trouble finding players with the facility and range to perform it. This resulted in a 1999 performance of the work with the Northwestern University Contemporary Music Ensemble. Rex has recorded solo albums of his own compositions for the d'Note and IGMOD labels. DownBeat magazine has printed that he "has an impressive touch: a sure command of tone and a gift for creating fetching modern harmonies," awarded his CD Pandora's Pocket three- and-a-half stars, and honored him in their International Critic's Poll as one of the top ten trumpeters deserving wider recognition. Cadence Magazine's review of Pandora's Pocket began, "Richardson is a trumpeter who combines the powerful stratospheric flights of Freddie Hubbard with the melodic bluesiness of Lee Morgan." The Chicago Tribune has extolled his "epic sound and rock solid technique" and says of his jazz playing that he "improvises with technical virtuosity in some passages, lyric poetry in others," describing his style as "a brilliant, technically audacious, rhythmically aggressive approach to improvisation."