Update 08/07/2019

Setting up the Digi-Gurdy to play via a mobile phone. 

I have now worked out how to play the melody via Channel 1 of a MIDI player running on a phone, the High D trompette via Channel 2, a Low G drone via Channel 3 and the crank-activated buzzing rhythm sound via Channel 4.

The MIDI player is free and called FluidSynth. The soundfont file (a library of sound effectively) that it uses is from the open source MIDI-gurdy project https://github.com/midigurdy/midigurdy to which I have added an extra buzzing sound.

By pressing the upper green button on the handle, the device behaves as if you are turning the crank handle, i.e. you get the drone sounds you have set up plus the open melody string (G4). You then play the melody via the keys while the drones continue to sound. 

In this version, the lower yellow button on the handle activates the buzzing trompette sound which is the rhythm section of a hurdygurdy, normally produced by momentary increases in rotation speed of the crank handle.

This means, in my next update, I can look at ways to simulate the crank handle by generation of a suitable voltage signal to the Arduino Teensy via a geared motor to which a crank handle has been attached.

I have also included in the video two quick bursts of the device running in demonstration mode just for fun.