Typically however, bebop musicians played tunes at much faster tempos. Soloists did not concern themselves as much with lyricism, but more with rhythmic unpredictability and harmonic complexity. It wasn’t just the soloists who were important, however. The advent of bebop marked an expansion of the roles of the rhythm section players, who were no longer simply time-keepers, but who interacted with the soloist with their own embellishments.