Recorded during the band's 1966 sessions, 'Rain' stands as a pivotal example of The Beatles' transition from pop to rock. The track features a distinctive, repetitive guitar riff that drives a hypnotic, almost industrial rhythm, showcasing George Harrison's growing compositional confidence. Released on the 'Past Masters' compilation, this recording captures the group's experimental spirit as they moved away from their earlier melodic structures toward more complex, groove-oriented arrangements. The song remains a defining piece of their late-period discography, illustrating their willingness to push musical boundaries and influence the development of hard rock and psychedelic genres.