Sound hardware

This section explains the sound hardware in NES/Famicom and some of the expansion chips found in some carts.
Internal 2A03/2A07 channels
The sound processor has five channels, two square waves, one triangle wave, one noise generator and one digital sample (DPCM) channel.
Square 1 & 2
Produces pulse waves with four duty settings (12.5%, 25%, 50% and 25% inverted). These channels have a hardware sweep unit that can be accessed by the H and I effects.
Note: There is a bug that resets the duty phase when switching between certain frequencies, this can be heard as a pop and might be noticable when using vibrato or pitch slides across those frequencies.
Triangle
Triangle shaped waveform. There is no volume control for this channel, however, due to how the hardware is implemented, the output level of the DPCM channel will affect the volume output of the triangle wave.
Noise
Noise generator. Can produce 32k-bit and 93-bit sequences, selectable from the instruments duty/noise setting.
DPCM (Delta PCM)
Used to play delta modulated samples. Most of the effects (like arpeggio & pitch slides) does not operate on this channel.
Expansion sound
The Famicom has the ability to mix sound from expansion chips found in some carts, famitracker now supports a few of those chips. Expansion sound is enabled from the module properties window.
Konami VRC6
The VRC6 chip has two square wave channels and one sawtooth wave channel. This chip was used in games like Akumajou Densetsu and Madara by Konami.
Square 1 & 2
Produces pulse waves like the internal channels, but have eight different duty settings and lacks hardware sweep.
Sawtooth
Sawtooth wave generator. This channel has no duty function but still uses that instrument setting to calculate the volume. A volume level too high will cause the wave to wrap around and sounds distorted (happens when duty = 1 and volume = 6).

Konami VRC7

The VRC7 chip contains a stripped down OPLL unit and has 6 channels for FM sound. This chip was used by Lagrange Point.

Nintendo FDS

This is a single channel chip used in the Famicom Disk System hardware by Nintendo. The channel uses a 64-step customizable waveform and has a simple frequency modulator.

Nintendo MMC5"> Nintendo MM The MMC5 chip has two square wave channels that are identical to the internal 2A03 channels except for no hardware sweep function. It was used in the game Just Breed by Enix.