Ricoh 2A03 microprocessor

The Ricoh 2A03 (RP2A03) is an 8-bit microprocessor that was created for the NES. Besides the CPU, it contains the console's sound hardware: five monophonic channels.12

  • 2 pulse waves: 4 duty cycles (12.5%, 25%, 50%, 75%), 16 volume levels, and a hardware pitch sweep. 25% and 75% sound the same.
  • Triangle wave: no volume control; it is either on or off.
  • Noise: 16 preset pitches in 2 modes. The second mode sounds more metallic.
  • Sample channel (DPCM): plays 1-bit delta-encoded samples.13

See Hardware limitations on NES audio for how composers worked within these channels.