It uses a routine PJRC audio board for good quality sound.
In this initial build, I've set it up to use a couple of oscillators, LP/HP filter, envelope generators etc so it's a very conventional virtual analogue instrument that plays by MIDI and USB. Version 01-01 will use band-limited oscillators. Version 01-02 will get Moog-style filters. Version 02-00 will go into additive synthesis (Walsh, Fourier et al), Karplus-Strong, Granular and possibly PM/FM too. And so on...
Also, whilst it doesn't play the hits of Bieber, you can hit him with it, should you feel the need.