The Famicom comes built in with the 2A03 chip, and has five audio channels: two square waves, one triangle wave, one noise generator, and one digital sample (DPCM) channel. On top of this, six expansions were created by both Nintendo and third parties. They are:

• Famicom Disk System sound: adds an extra channel with custom wavetable capabilities. (Example: Zelda, Metroid, etc. Most but not all Disk System games)
• Nintendo MMC5: Adds two square waves identical to the 2A03 square waves and a PCM channel. This is the only expansion that the international NES could use. (Example: US/European Castlevania III)
• Konami VRC6: Adds two square waves but has 8 duty cycles (voices) instead of the standard 4. Also adds a sawtooth wave. (Example: Akumajou Densetsu (Japanese Castlevania III)
• Konami VRC7: Adds six FM channels with 15 built-in patches (instruments) and the ability to create 64 unique patches. (Example: Langrage Point)
• Namco 163: Adds up to eight channels with definable waves. (Example: Digital Devil Story: Megami Tensei II)
• Sunsoft 5B: Adds 3 50% pulse waves (stuck on one voice). Can be manipulated to generate noise, sawtooth, or triangle waves. (Example: Gimmick!)