A certain nostalgia for the south developed; but at the same time, the transplanted
Blacks were becoming more sophisticated, preferring to listen to music played by
musicians more sophisticated than the rural blues performers. Thus small blues
combos, with piano, guitar, harmonica and other instruments, began to replace the
solo performers. From the 40's onwards, they converted to electric instruments, and
began to play a new form of blues, louder, more aggressive, which came to be called
"urban blues". In the 50's, Muddy Waters and Howlin' Wolf were among the
major exponents of this type of music, and later served as models imitated by many
sixties groups such as the Rolling Stones and the Animals.