The Beatles made innovative use of technology, treating the studio as an instrument in itself. They urged experimentation by Martin and their recording engineers, regularly demanding that something new be tried because "it might just sound good".
Many of the Beatles could play more than one instrument.
This photograph shows Paul McCartney's 4-stringed sunburst bass guitar on the left, and George Harrison's 6-string red guitar on the right.
The album "Help!" saw the band making increased use of vocal overdubs and incorporating classical instruments into their arrangements, notably the string quartet on the pop ballad "Yesterday".