 The original Mellotrons were intended to be used in the home or in clubs , and were not designed for touring bands . Even the later M400 , which was designed to be as portable as possible , weighed over 122 pounds ( 55 kg ) . Smoke , and variations in temperature , and humidity were also detrimental to the instrument 's reliability . Moving the instrument between cold storage rooms and brightly lit stages could cause the tapes to stretch and stick on the capstan . Leslie Bradley recalls receiving some Mellotrons in for a repair " looking like a blacksmith had shaped horseshoes on top . " Pressing too many keys at once caused the motor to drag , resulting in the notes sounding flat . Robert Fripp stated that " Tuning a Mellotron doesn 't " . Dave Kean , an expert Mellotron <unk> , recommends that older Mellotrons should not be immediately used after a period of inactivity , as the tape heads can become magnetized in storage and destroy the recordings on them if played . 
