Robert Moog revolutionized music with the invention of the first commercial modular synthesizer. His breakthrough was the use of Voltage-Controlled Oscillators (VCOs) and filters, which allowed musicians to change the pitch and timbre of electronic sounds using electrical signals rather than manually turning heavy dials. The Moog synthesizer became a mainstream sensation with Wendy Carlos's 1968 album 'Switched-On Bach,' which proved that electronic instruments could be used for expressive classical music. Later, the Minimoog became the first 'portable' synth with a built-in keyboard, becoming a staple for rock and funk musicians like Keith Emerson and Bernie Worrell.