Website: electrotechnique.cc
The pcb and front panel to build TSynth are available from Tindie with SMD 4067 multiplexers, 6N137 opto-isolator, capacitors and resistors fitted. The entire cost of parts to build TSynth will be around $99 if you buy components from the cheaper suppliers and the build time around two hours to solder. Plans for a 3D printed/laser cut enclosure are also available. Questions: info@electrotechnique.cc
Format your SD card using the SD Association formatter. Copy all the presets straight on to the card with no other files or folders.
The source code requires the latest Teensyduino from PJRC to compile. You also need CircularBuffer from Agileware and Adafruit_GFX, which are available in the Arduino Library Manager.