Final answer:
The difference between R&B and Rock & Roll in 1951 revolved around their audiences and thematic expressions. R&B was rooted in Black musical traditions and initially aimed at Black audiences.
Step-by-step explanation:
In 1951, the differences between R&B and Rock & Roll were beginning to take shape. R&B, or Rhythm and Blues, was a genre that emerged from a confluence of uptempo blues, jazz, and country music, predominantly created by Black artists and initially marketed towards Black audiences.
Rock & Roll, inspired by R&B, began to celebrate themes like young love and freedom, quickly gaining popularity among young White audiences, which had not been the traditional market for R&B.
The genre was propelled to wider audiences through influencers like Alan Freed who popularized Rock & Roll through radio play and live concerts. Icons such as Sister Rosetta Tharpe and Jackie Brantson were pivotal figures in the burgeoning Rock & Roll scene, which borrowed heavily from the sounds and styles of R&B.
Throughout the 1950s, Rock & Roll music was on the defensive from certain quarters. Many parents and figures like Frank Sinatra deemed it a threat to 'American values', fearing its influence and the breaking of racial barriers it represented.
Despite adult reservations, the youth embraced Rock & Roll, which also had lasting social implications. Not only did it foster social mingling of black and white teenagers but also contributed to the advancement of civil rights by bringing together disparate cultural groups.
The 1950s were a transformative era for music, largely due to new technology such as the solid-body electric guitar and the spread of television, shows like The Ed Sullivan Show and American Bandstand helped popularize the genre further.
Rock & Roll artists, including Little Richard and Chuck Berry, brought their unique sounds to a much wider and more diverse audience, which contributed considerably to the genre's popularity and profitability.