Apple II sound cards
The Apple II had limited inherent sound capabilities until the Apple //gs shipped in 1986. Many third-party manufacturers made sound cards to enable richer sound output.
Music cards consist primarily of circuit boards plugged into the expansion slots of the Apple computer. There is generally no method to directly play the cards as a musical instrument. Instead, music is programmed into the computer, typically using the computer's keyboard and pointing devices (such as the Apple's game controls or using an add-on light pen). The computer then plays the music back using the music cards to produce the sound, generally through a standard audio system.
ALF Music Card MC16
The first hardware music accessory for the Apple II was ALF's "Apple Music Synthesizer", later renamed "Music Card MC16". It was demonstrated late in 1978 and began shipping in volume June 1979. It featured graphical music entry, a first for any personal computer. Each card produced three voices, and two or three cards could be used for six or nine voices.
ALF Music Card MC1
Using much the same software as the ALF Music Card MC16, ALF introduced a new hardware design as the "Apple Music II", later renamed "Music Card MC1". It had nine voices on a single card, although the range, tuning accuracy, and envelope/volume control was reduced compared to the Music Card MC16. The card used three TI SN76489N chips.
Mountain Computer Music System
Music systems generally include all the features of music cards, but add a method of playing the instrument directly (usually a piano-style keyboard). This allows music to be played "live", and the notes can also be captured by the computer for subsequent playback or editing and playback.
The Alpha Syntauri was a music system designed around the expansion capabilities of the Apple ][. The hardware consisted of an external piano-style keyboard and cards that plugged into the Apple ][ (a keyboard interface card and music synthesizer cards). Originally the music synthesizer was ALF's Apple Music Synthesizer, and later the two-board Mountain Computer Music System was used. Software was designed to support music composition and performance. Herbie Hancock and Keith Emerson were notable early adopters of the Syntauri system. 
Passport Designs Soundchaser
The Passport Designs Soundchaser Computer Music System provided similar capabilities, but the software emphasized composition over real-time performance. The Soundchaser included a 49-key keyboard, keyboard interface card, and a choice of sound cards depending on whether the digital or analog option was chosen. The digital option included the Mountain Computer Music System cards.
- Alpha Syntauri system used in software demo
- ALF Products advertisement, "Apple Music", Creative Computing, Vol. 6 No. 2, Feb. 1980 pg. 103. Retrieved 2013-04-11.
- North, Steve, "ALF/Apple Music Synthesizer", Creative Computing, Vol. 5 No. 6, June 1979 pg. 102. Retrieved 2013-04-11.
- Jigour, Robin; Kellner, Charlie; Lapham, Ellen. "The alphaSyntauri Instrument: A Modular and Software Programmable Digital Synthesizer System". Philadelphia: IEEE Computer Society, 1981.
- Vail, Mark. Vintage Synthesizers, p. 91-92. San Francisco: Miller Freeman Books, 2000
- Hogan, Thom (1981-07-27). "Two keyboard synthesizers for Apple". InfoWorld.