How did music change from the 50s to the 60s?

Let's just take rock and roll for example. I guess it really bloomed in the mid 50s when you had people like Elvis Presley, Jerry Lee Lewis and Carl Perkins. You had white boys playing their version of blues that they had learned on the radio or from other blues artists, and then mixing that with the country and western roots from their hometown. That essentially became rock and roll; a mixture of blues and country music. But we still had people who were singing other people's songs. Only a couple of artists like Little Richard wrote their own songs. Elvis still did other people's songs. Moving into the 60s though, that started changing a little bit. You still had plenty of pop stars and other rock stars making money off of other people's songs, but with the mainstream success of Bob Dylan and The Beatles, both of whom wrote their own material, they made music more and more artistic. Self expression became important whereas before we did not really have an artist coming in and demanding control of how the record was produced, mixed what the cover out would be and what the song sequence would be. Elvis, and people like that, were strictly performers. By the mid 60s though, you had all these bands and artists really demanding their own artistic freedom.