I used to produce one for the NES: https://github.com/jareklupinski/chip-maestro / https://www.kickstarter.com/projects/jarek/chip-maestro-an-n...

Though if you're serious about using it for music production, I recommend popping the CPU out and dropping it into a dedicated board so you're not dealing with stuff like cartridge grime issues in a studio: https://github.com/jareklupinski/standalone-nes-synth