by Romain Michon
The Blade Axe is a physical modeling instrument that uses an ipad for all of the synthesis. It has gone through many iterations but the current version uses two piezo sensors to pick up the plucking for melody and chords.
You can find more of Romain’s work here:
https://ccrma.stanford.edu/~rmichon/
Max Hack: After many different iterations of sensors and micro-controllers, Romain actually simplified the input into two piezos that output audio signals which go directly into the audio input of the ipad. This means that no other micro-controllers or embedded boards were needed and the signal from the piezos is kept at audio rates, improving the input to the physical model.