Johnny Hartman....

Despite his talents, jazz singer Johnny Hartman struggled to maintain a thriving career. Hartman caught a couple of big breaks during his life that seemed to show promise, but the racial and cultural milieu during his active years were such that he never earned the recognition he deserved while he was still alive.
Hartman’s first big opportunity came after he won a singing competition at age 17 in a Chicago supper club. The prize was a brief engagement with Earl Hines’ big band. Hines, whose band cultivated the talents of bebop stars such as Charlie Parker and Dizzy Gillespie, invited Hartman to join the group for a longer period.

Bebop: Not the Right Fit:
Hartman, whose strengths were his dulcet vocal timbre, emotional nuances, and meticulous phrasing, did not entirely fit into the bebop scene. He left Hines’ band to sing in Gillespie’s big band, but abandoned it in 1949 for a solo career.
Hartman distinguished himself from the majority of jazz singers in the 1950s by rejecting conventions such as scat singing and modifying standard songs. He prided himself on staying close to original melodies, allowing the lyrics to guide his musical interpretation. Some argue that for this reason, Hartman’s potential was squelched by promoters who weren’t interested in supporting a black musician who sounded thoughtful, intelligent, and romantic.
http://jazz.about.com/od/classicjazzartists/p/JohnnyHartman.htm