This is a single channel chip used in the Famicom Disk System hardware by Nintendo. It was an external disk drive unit available for Famicom, games was distributed on disks instead of carts.
The channel uses a 64-step customizable waveform and has a simple frequency modulator.
The instrument editor allows to edit the custom waveform, either with the mouse or by changing the Wave-textbox. Four default waveforms are available: sine, triangle, square and sawtooth.
The rest of the controls belongs to the frequency modulator: rate (0 - 4095), depth (0 - 63) and delay (0 - 255) after a note is triggered can be set. (This is copied straight from MCK). The big box is the modulation table, where each box tells how much to add or subtract from the frequency. Each value is used twice by the modulator unit, and the frequency is automatically reset each time end is reached. Yellow = 0, green above = +1, +2, +5, green below = -1, -2, -4 and blue is reset to initial frequency.
There is also a tab with envelopes for volume, arpeggio & pitch.