I built a simple synth in Pure Data to make chiptune music! A quick project and nothing special here, but I just wanted to create some retro sounds from scratch. The synth has four channels with two PWM modules, one triangle wave synth module and some noise generators for drums.
The song is composed and running in a DAW which sends four channels of MIDI to Pd via IAC driver. In addition to MIDI notes the synth understands modulation wheel values and translates them into vibrato.
EDIT (January 25, 2019): Here are two other simple chiptune tracks made with the synth. I didn't tweak the sounds at all, so sonically they are very similar to the example above.