Marco De Vivo demonstrates (video) with his MDV microSynth even a fairly simple Teensy-based synth leveraging the Teensy Audio Library can produce excellent results!

In this project he creates a powerful instrument from a Teensy and Audio Adapter, plus an LCD display, potentiometer, a 5-Pin DIN MIDI jack, and a few buttons — all on a breadboard!

We weren’t able to find a ton of info beyond the video below, which gives a great demonstration of its capabilities. The synth is monophonic with four oscillators, low and high-pass filters, ADSR envelope control, and various effects including stereo delay, portamento, and morphing via modulation wheel.