The AY Teletalk box is basically a classic 1970's arcade game synthesizer chip, the AY-3-8912, controlled by an Arduino Uno microprocessor.
An Arduino Template program provides all the functions needed to access the chip's 14 registers that control the 3 squarewave/noise voices.
A forth voice comes from the Arduino. Each voice has a volume pot and modulation capabilities. Three switches and slide pots can be programmed as controllers.