[Otermrelik] wanted to experiment with the Teensy audio library and adapter. That, combined with his 3D printer, led to a very cool looking build of the teensypolysynth. The device looks like a little mini soundboard with sliders and 3D printed knobs. You can see (and hear) it in the video below.
The Teensy audio library supports several output devices including several built-in options and external boards like the audio adapter used here. The library does CD-quality sound, supports polyphonic playback, recording, synthesis, mixing, and more.