are an English rock band formed in London in 1964. Their classic lineup (1964–1978) consisted of lead vocalist Roger Daltrey, guitarist Pete Townshend, bassist John Entwistle and drummer Keith Moon. They are considered one of the most influential rock bands of the 20th century, and have sold over 100 million records worldwide. Their contributions to rock music include the development of the Marshall stack, large public address systems, the use of synthesisers, Entwistle's and Moon's influential playing styles, Townshend's feedback and power chord guitar technique, and the development of the rock opera. They are cited as an influence by many hard rock, punk, power pop and mod bands. The Who were inducted into the Rock and Roll Hall of Fame in 1990.