Some forms of performed music are expected to use a certain language or type of language. For example, in the 17th century, operas were expected to be in Italian, the language of origin of this type of music — even if the writer was German.
American popular music of the 1940s that was directed to an audience of white Americans used standard English — for example, such standards as "Autumn Leaves" or "Stardust." American popular music of this period that was created by or directed to an African-American audience was derived from the African-American forms jazz music and blues music, and used grammatical forms that were, and are, correct in the dialect used by that audience, African-American English Vernacular (AAEV or "Black English"), but that are not Standard English.
Rock and Roll music grew out of Rhythm and Blues music, which grew out of Blues music. Rock and Roll songs are expected to use some characteristics of AAEV, or else they don't "sound right." Even the Beatles, from Liverpool, write that "She's got a ticket to ride, and she don't care." In Rock and Roll lyrics you can hear many features of AAEV, such as rhyming "know" with "more", pronounced "mo", as in "I know, you don't love me no mo'," or the use of the double negative, as in "I can't get no satisfaction." Bjork, from Iceland, writes "You just ain't receiving." If this sort of thing were not done, the Rock and Roll would sound as if it were being sung by pedantic accountants - it would sound "too white."