Another new thing in rock music was experimenting with sounds. Roxy Music introduced an oboe to rock. And when Pink Floyd wondered what a piano would sound like through a Leslie speaker, they came up with the intro to Echoes, a piece that lasted the entire second side of the album "Meddle." The stage performances of songs could also last much longer than the album versions. The performances grew so large that Pink Floyd felt ever more alienated from the audience and decided to 'protest' against that by putting up such a large performance with huge puppets for the stage show of The Wall that the band became almost invisible. During the show they built up a wall on stage between themselves and the audience making them literally invisible. This performance lasted only four shows and marked the end of this age of rock.