"The Chip Maestro is a finished product up
on Kickstarter, and it's seeking backers!
The Chip Maestro is a special NES cartridge that turns the NES into a synthesizer. You can play it using a MIDI keyboard or a USB to MIDI converter. By directly manipulating the NES CPU's sound circuitry, all sounds played through this cartridge are authentic NES tones! This is as realistic to the 8-bit era as you can get with live sound. Previous trackers have been able to play music, but all of them required pre-composition. This cartridge lets you do improvs and solos during live shows, or fiddle around with new tunes. I hope to get it into every chiptune artist's hands soon. Thanks for your support!"
Update via Jarek: "The advantage of the Chip Maestro over the MIDInes is its availability and price.
The Chip Maestro will support parameter changes to all sound channels of the NES. If you pledge at any level, you will get first look at the technical documents, and be able to propose changes/improvements that you would like, such as which parameter changes are important, and how they would be best implemented."