While the Beatles still largely stuck to love songs on Rubber Soul, the lyrics represented a quantum leap in terms of thoughtfulness, maturity, and complex ambiguities. Musically, too, it was a substantial leap forward, with intricate folk-rock arrangements that reflected the increasing influence of Dylan and the Byrds. The group and George Martin were also beginning to expand the conventional instrumental parameters of the rock group, using a sitar on "Norwegian Wood (This Bird Has Flown)," Greek-like guitar lines on "Michelle" and "Girl," fuzz bass on "Think for Yourself," and a piano made to sound like a harpsichord on the instrumental break of "In My Life." While John and Paul were beginning to carve separate songwriting identities at this point, the album is full of great tunes, from "Norwegian Wood (This Bird Has Flown)" and "Michelle" to "Girl," "I'm Looking Through You," "You Won't See Me," "Drive My Car," and "Nowhere Man" (the last of which was the first Beatle song to move beyond romantic themes entirely). George Harrison was also developing into a fine songwriter with his two contributions, "Think for Yourself" and the Byrds-ish "If I Needed Someone."