 The techniques initially used by the Radiophonic Workshop were closely related to those used in "musique concrète"; new sounds for programs were created by using recordings of everyday sounds such as voices, bells or gravel as raw material for "radiophonic" manipulations.In these manipulations, audio tape could be played back at different speeds (altering a sound's pitch), reversed, cut and joined, or processed using reverb or equalisation.The most famous of the Workshop's creations using 'radiophonic' techniques include the "Doctor Who" theme music, which Delia Derbyshire created using a plucked string, 12 oscillators and a lot of tape manipulation; and the sound of the TARDIS (the Doctor's time machine) materialising and dematerialising, which was created by Brian Hodgson running his keys along the rusty bass strings of a broken piano, with the recording slowed down to make an even lower sound.