Website: electrotechnique.cc
The pcb and front panel to build TSynth will be available around May 2020 from Tindie with SMD 4067 multiplexers, 6N138 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 will be available. Questions: info@electrotechnique.cc
The source code requires Teensyduino from PJRC to compile. You also need to put the files in Modified Libraries into the Teensy Audio folder to replace the installed versions. You also need CircularBuffer from Agileware, which is available in the Arduino Library Manager.