The complete designs (PCB, bill of materials, firmware source code) for the discontinued MIDISpeak and MIDI2600 products have been posted under the Creative Commons Attribution license. The license allows anyone to manufacture these products for personal use or for profit.
The source files can be found at the Highly Liquid Forum:
For those interested in Atari 2600 retrofits, the MD24 (joystick control) or UMR2 (keypad control) can be used.
The NTH is a fun-to-use, sonically-rich, hackable music synthesizer. It features digital oscillators, an analog low-pass filter, an integrated step sequencer, MIDI I/O, and simple, intuitive controls.
The NTH is available for purchase from February 2, 2012 to March 1, 2012 via Kickstarter:
Upon successful funding, production of the NTH will begin and the entire design will be open-sourced.
Audio examples, product photos, and additional documentation can be found at the NTH website:
The NTH was designed by Kevin Holland (sineqube.com) and John Staskevich (highlyliquid.com).
The design for a MIDI2600 enclosure has been posted. The engraved aluminum panel can be ordered from Front Panel Express. Like the MIDI2600-External, the enclosure can be connected to an Atari 2600 via joystick extension cables.