Complex sentence: He started playing bass at the age of 15 when he became friends with a drummer and a guitar player, they were looking for a bass player so he bought his first bass and started jamming with covers of the Sex pistols, The Ramones and others.
Split into simpler sentences: He started playing bass at the age of 15 when he became friends with a drummer and a guitar player. They were looking for a bass player so he bought his first bass and started jamming with covers of the Sex Pistols, the Ramones and others.