Mantra is a piece created by composer Karlheinz Stockhausen. It involves the use of two piano’s, the sounds of which are ring modulated. Each piano player makes use of a simple control box to allow them to control the frequency of the modulator. While originally the modulation was performed using analog electronics, this current version will perform the modulation in software, using Max/MSP. My part in the project is to design the control boxes and their interface to allow the performers to control the ring modulation.