Complex sentence: His primary instrument is the piano (frequently prepared piano) which he explores through manipulating it's sound with use of various electromagnetic string stimulators like ebows (which he pioneered from 1991), and motorized actuators.
Split into simpler sentences: His primary instrument is the piano (frequently prepared piano). He explores the possibilities of the piano, manipulating it's sound with use of various electromagnetic string stimulators like ebows, and motorized actuators.