Complex sentence: They need a drummer and a manager, and although Sutcliffe can sing, he cannot play an instrument, only being in it because he is John's friend and none of the others want to play the bass guitar.
Split into simpler sentences: They need a drummer and a manager, and although Sutcliffe can sing, he cannot play an instrument. The only reason Stu is in the band because he is John's friend and none of the others want to play the bass guitar.