Explain briefly why some rock music was nicknamed 'soul.'

According to the Rock and Roll Hall of Fame, soul is "music that arose out of the black experience in America through the transmutation of gospel and rhythm & blues into a form of funky, secular testifying". Catchy rhythms, stressed by handclaps and extemporaneous body moves, are an important feature of soul music. Other characteristics are a call and response between the lead vocalist and the chorus and an especially tense vocal sound. The style also occasionally uses improvisational additions, twirls and auxiliary sounds. Soul music reflected the African-American identity and it stressed the importance of an African-American culture. The new-found African-American consciousness led to new styles of music, which boasted pride in being black.

Soul music dominated the U. S. R&B chart in the 1960s, and many recordings crossed over into the pop charts in the U. S., Britain and elsewhere. By 1968, the soul music genre had begun to splinter. Some soul artists developed funk music, while other singers and groups developed slicker, more sophisticated, and in some cases more politically conscious varieties. By the early 1970s, soul music had been influenced by psychedelic rock and other genres, leading to psychedelic soul. The United States saw the development of neo soul around 1994. There are also several other subgenres and offshoots of soul music.

According to the Rock and Roll Hall of Fame, soul is "music that arose out of the black experience in America through the transmutation of gospel and rhythm & blues into a form of funky, secular testifying" ... The new-found African-American consciousness led to new styles of music, which boasted pride in being black.