Editing Commodore 64 (section)

=== Sound ===

The SID chip has three channels, each with its own [[ADSR envelope]] generator and filter capabilities. [[Ring modulation]] makes use of channel three to work with the other two channels. [[Bob Yannes]] developed the SID chip and, later, co-founded the synthesizer company [[Ensoniq]]. Composers and programmers of game music on the C64 include [[Rob Hubbard]], [[Jeroen Tel]], [[Tim Follin]], [[David Whittaker (video game composer)|David Whittaker]], [[Chris Hülsbeck]], [[Ben Daglish]], [[Martin Galway]], Kjell Nordbø and David Dunn. Due to the chip's three channels, chords are often played as [[arpeggio]]s. It was also possible to continuously update the master volume with sampled data to enable the playback of 4-bit digitized audio. By 2008, it was possible to play four-channel 8-bit audio samples and two SID channels and still use filtering.<ref>{{cite web|title=New revolutionary C64 music routine unveiled|publisher=C64Music!|year=2008|url=http://c64music.blogspot.com.au/2008/11/new-revolutionary-c64-music-routine.html|access-date=May 20, 2014}}</ref>

[[File:StrikeForce8580R5.ogg|thumb|alt=Electronic-music clip|An example of SID chip-generated music]]
There are two versions of the SID chip: the 6581 and the 8580. The [[MOS Technology 6581]] was used in the original ("breadbin") C64s, the early versions of the 64C, and the [[Commodore 128]]. The 6581 was replaced with the MOS Technology 8580 in 1987. Although the 6581 sound quality is a little crisper, it lacks the 8580's versatility; the 8580 can mix all available waveforms on each channel, but the 6581 can only mix waveforms in a channel in a limited fashion. The main difference between the 6581 and the 8580 is the supply voltage; the 6581 requires {{nowrap|12 volts}}, and the 8580 {{nowrap|9 volts}}. A modification can be made to use the 6581 in a newer 64C board (which uses the {{nowrap|9-volt}} chip).

In 1986, the Sound Expander was released for the Commodore 64. It was a [[sound module]] with a [[Yamaha YM3526]] chip capable of [[FM synthesis]], primarily intended for professional [[music production]].<ref>{{cite magazine |last1=Taylor |first1=Graham |title=Music Hardware: Now that's what I call music |magazine=[[Popular Computing Weekly]] |date=February 13, 1986 |pages=13–4 |url=https://archive.org/details/popular-computing-weekly-1986-02-13/page/n12}}</ref><ref name="Yamaha">{{cite web |title=Yamaha Sound Chips |url=https://soundprogramming.net/electronics/yamaha-sound-chips/ |website=Sound Programming |access-date=October 9, 2020}}</ref>