Although Harrison's role as lead guitarist was limited during the sessions, Everett considers that "his contribution to the album is strong in several ways." He provided Indian instrumentation in the form of sitar, tambura and swarmandal, and Martin credited him with being the most committed of the Beatles in striving for new sounds. Starr's adoption of loose calfskin heads for his tom-toms ensured his drum kit had a deeper timbre than he had previously achieved with plastic heads. As on "Revolver", the Beatles increasingly used session musicians, particularly for classical-inspired arrangements. Norman comments that Lennon's prominent vocal on some of McCartney's songs "hugely enhanced their atmosphere", particularly "Lovely Rita".