The Okay 2 is an open source, 3D printed synthesizer.
It is a simple monophonic synth design, with two octaves of mini-keys and a 1/4″ audio output jack.
Here’s what the developer has to say about it:
Monophonic: Only one note at a time can be played. This is opposed to “polyphonic,” where multiple simultaneous notes can be played.
Analog: There are no computers, microcontrollers, sound samplers, or anything digital involved. The sound you hear is the sound of a speaker being abused by discrete electronic components like capacitors and resistors and logic chips.
Square-wave: When its output is viewed on an oscilloscope, its wave resembles a square. It’s a “hard” sounding wave type, great for bass lines, and commonly associated with chiptune music and old video games.
Because it’s an open source DIY project, you can change the colors and adapt the design as you like.