 The Mellotron has a similar behaviour to a sampler , but generates its sound via audio tape . When a key is pressed , a tape connected to it is pushed against a playback head , like a tape recorder . While the key remains depressed , the tape is drawn over the head , and a sound is played . When the key is released , a spring pulls the tape back to its original position . A variety of sounds are available on the instrument . On earlier models , the instrument is split into " lead " and " rhythm " sections . There is a choice of six " stations " of rhythm sounds , each containing three rhythm tracks and three fill tracks . The fill tracks can also be mixed together . Similarly , there is a choice of six lead stations , each containing three lead instruments which can be mixed . In the centre of the Mellotron , there is a tuning button that allows a variation in both pitch and tempo . Later models do not have the concept of stations and have a single knob to select a sound , along with the tuning control . However , the frame containing the tapes is designed to be removed , and replaced with one with different sounds . 
