In their new songs, the Beatles drew inspiration from soul music, particularly the singles they heard on US radio that summer, by acts signed to the Motown and Stax record labels, and from the contemporary folk rock of Dylan and the Byrds. Author Robert Rodriguez highlights the Byrds as having achieved "special notice as an American act that had taken something from the Brits, added to it, then sent it back". In doing so, Rodriguez continues, the Byrds had joined the Beatles and Dylan in "a common pool of influence exchange, where each act gave and took from the other in equal measure". According to music critic Tim Riley, "Rubber Soul" served as a "step toward a greater synthesis" of all the elements that throughout 1965 represented a "major "rock 'n' roll" explosion", rather than just the emergence of folk rock. Citing Dylan and the Rolling Stones as the Beatles' artistic peers during this period, he says that on "Rubber Soul" these two acts "inspire rather than influence their sound".