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.

This project makes use of my AVR-HID device to allow the performers to interact with the system. Each performer has a control box which contains a single potentiometer and a switch. The boxes receive power from the main AVR-HID box and return a voltage signal based on the current value of the potentiometer and the switches. The AVR-HID converts these voltages to digital values with 10-bit precision at a rate of 100Hz and makes them available to the software over a USB connection.

Each controller consists of a large plastic project box which contains a control knob and a small switch. On the side of each box is the connection to the main AVR-HID device. In order to allow for different performance situations, the boxes are connected using standard XLR cables, which are generally readily available at any concert location. Here is a photo of the final physical interfaces designed for this project. More photos are available in the mantra gallery.