The electric guitar changed the economics of music

Before amplification, a live musician's reach was limited by how far sound could carry. A 19th-century pianist could perform for perhaps 2,000 people at most. The electric guitar, commercially popularised in the 1930s and reaching mass adoption with Les Paul and Leo Fender's innovations in the early 1950s, meant a single performer could fill a stadium of 100,000. Combined with recording and broadcast, it transformed music from a live, local experience into a global medium — and changed the economics from multiple local musicians earning modest livings to a handful of global stars earning vast fortunes, with consequences for the entire music industry.

Source: Millard, The Electric Guitar: A History of an American Icon (2004)