Throughout the 1960s Hubbard played as a sideman on some of the most important albums from that era, including Oliver Nelson's "The Blues and the Abstract Truth", Eric Dolphy's "Out to Lunch!", Herbie Hancock's "Maiden Voyage", and Wayne Shorter's "Speak No Evil". Hubbard was described as "the most brilliant trumpeter of a generation of musicians who stand with one foot in 'tonal' jazz and the other in the atonal camp". Though he never fully embraced the free jazz of the 1960s, he appeared on two of its landmark albums: Coleman's "" and Coltrane's "Ascension", as well as on Sonny Rollins' "new thing" track, "East Broadway Run Down" (on the 1966 album of the same name), with Elvin Jones and Jimmy Garrison.