Platform - Computer » Apple II Series (pre-Apple IIgs)
This song platform is for music made on all "pre-Apple llgs" Apple ll's.
The first Apple ll was released in 1977 and did not have any special sound capabilities but could be upgraded with soundcards and the most popular one was the "Mockingboard".
Early version of Mockingboard has only one AY-3-8910 soundchip (3-channel PSG), later versions has two AY chips giving a total 6-channels of PSG.
There was also a Mockingboard-compatible called "Phasor" wich had four AY soundchips, even if it gave 12 channels of PSG so did not many games use that.
More info here about possible soundcards for Apple ll: