Complex sentence: The introduction of the multitrack recording system had a major influence on rock music, because it enabled record producers to overdub many layers of instrument tracks and vocals, creating new sounds that would not be possible in a live performance.
Split into simpler sentences: The introduction of the multitrack recording system had a major influence on rock music, because it could do much more than record a band's performance. Using a multitrack system, a band and their music producer could overdub many layers of instrument tracks and vocals, creating new sounds that would not be possible in a live performance.