A Fifth Voice For Atari
I have had an Atari 800 for quite a while now, and love it. Also, being a musician, I like working with the Atari sounds and Music Composer. One thing that intrigues me is the Apple's ability to produce sounds through its internal speaker. Even though I have no need for this on the Atari, I want to know if this is possible, perhaps to produce a fifth voice, or even stereophonic sound.
The internal speaker on the Atari 400 and 800 can be programmed in much the same way as the Apple. If you POKE 53279 with a 0, the internal speaker will emit a small click. The operating system turns off the speaker within 1/60 second, during the periodic vertical blank. Every time you POKE 53279,0 to pop out the speaker, the OS (operating system) pops it back in.
If you disable the vertical blank, you can push or pop the speaker at your own rate. Machine language is required to click the speaker fast enough to generate tones. An article and program to use the internal speaker as a "fifth voice" can be found in COMPUTE!'s Second Book of Atari: "The Atari Keyboard Speaks Out."
Incidentally, the new XL computers do not have an internal speaker. All access to location 54018 is routed to the TV or monitor speaker.