Square wave with 4 duty cycle settings and hardware sweep
Square wave with 4 duty cycle settings and hardware sweep
Triangle wave, often used for bass lines and smooth tones
Pseudo-random noise generator for percussion and effects
Delta pulse-code modulation channel for low-fidelity sampled audio
The NES/Famicom uses the Ricoh 2A03 (NTSC) or 2A07 (PAL) — a custom chip integrating a 6502-compatible CPU with a 5-channel APU: 2 pulse waves, a triangle, a noise generator, and a DPCM sample channel. The PAL 2A07 runs at a slightly lower clock rate, causing subtle pitch and tempo differences in PAL releases. Famicom cartridges could also add expansion audio chips (VRC6, VRC7, FDS, MMC5, Namco 163) not available on Western NES hardware.