The songs demonstrate the Beatles' increasing maturity as lyricists, and in their incorporation of brighter guitar tones and new instrumentation such as sitar, harmonium and fuzz bass, the group striving for more expressive sounds and arrangements for their music. The project marked a progression in the band's treatment of the album format as an artistic platform, an approach they continued to develop with "Revolver" and "Sgt. Pepper's Lonely Hearts Club Band". The four songs omitted by Capitol, including the February 1966 single "Nowhere Man", later appeared on the North American release "Yesterday and Today".