a style more strongly influenced by blues-rock pioneers, and were starting to play with an intensity and drive seldom found in white American acts; this influence would go on to shape the future of rock music through the British Invasion. Pop rock and instrumental rock The term pop has been used since the early 20th century to refer to popular music in general, but from the mid-1950s it began to be used for a distinct genre, aimed at a youth market, often characterized as a softer alternative to rock and roll. From about 1967, it was increasingly used in opposition to the term rock music, to describe a form that was more commercial, ephemeral and accessible. In contrast rock music was seen as focusing on extended works, particularly albums, was often associated with particular sub-cultures (like the counterculture of the 1960s), placed an emphasis on artistic values and "authenticity", stressed live performance and instrumental or vocal virtuosity and was often seen as encapsulating progressive developments rather than simply reflecting existing trends. Nevertheless, much pop and rock music has been very similar in sound, instrumentation and even lyrical content. The period of the later 1950s and early 1960s has traditionally been seen as an era of hiatus for rock and roll. More recently some authors have emphasised important innovations and trends in this period without which future developments would not have been possible. While early rock and roll, particularly through the advent of rockabilly, saw the greatest commercial success for male and white performers, in this era, the genre was dominated by black and female artists. Rock and roll had not disappeared at the end of the 1950s and some of its energy can be seen in the Twist dance craze of the early 1960s, mainly benefiting the career of Chubby Checker. Also significant was the advent of soul music as a major commercial force. Developing out of rhythm and blues with a re-injection of gospel music and pop, led by pioneers like Ray Charles and Sam Cooke from the mid-1950s, by the early 1960s figures like Marvin Gaye, James Brown, Aretha Franklin, Curtis Mayfield and Stevie Wonder were dominating the R&B charts and breaking through into the main pop charts, helping to accelerate their desegregation, while Motown and Stax/Volt Records were becoming major forces in the record industry. Some music historians have also pointed to important and innovative technical developments