Complex sentence: The new sub-genre of pop and rock known as psychedelic music started becoming completely mainstream after 1966, with the release of The Beatles's album "Revolver" providing regular audiences with sounds such as those in the song "Tomorrow Never Knows".
Split into simpler sentences: The new sub-genre of pop and rock known as psychedelic music started becoming completely mainstream during the former decade. After 1966, with the release of The Beatles's album "Revolver", regular audiences embraced eccentric sounds such as those in the song "Tomorrow Never Knows".