Final answer:
George Clinton is the musician who defined funk post-James Brown and led Parliament and Funkadelic, whereas Alan Freed is the disc jockey known for popularizing rock and roll.
Step-by-step explanation:
The man who defined the style known as funk post-James Brown and simultaneously led the bands Parliament and Funkadelic was George Clinton. These bands were central to the funk music movement, and George Clinton is renowned for his innovative sound that blends elements of psychedelic rock, soul, and funk. Meanwhile, the disc jockey credited with popularizing rock and roll is Alan Freed, who used the phrase “rock and roll” on mainstream radio and organized the first rock and roll concert, thus having a significant impact on the genre's reach and popularity.