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Music/Sound

Four voices of 8-bit pitch-resolution, 4-bit volume-resolution, 8-distortion sound can be produced. 2 voices (1 and 2, and/or 3 and 4) can be combined to make 16-bit pitch-resolution. Also 4-bit volume-only modes can be enabled for digitally sampled sound replay.

A fifth "voice" is produced by the internal speaker on Atari 400/800's (for keyclick and buzzer) and in the XL's and XE's this was (fortunately!) rerouted through the normal audio output, and the keyclick can be disabled.

POKEY (means "POT and KEY" as in the paddles and keyboard) is a digital input/output (I/O) chip. It handles such disparate tasks as the serial I/O bus, audio generation, keyboard scan, and random number generation. It also digitizes the resistive paddle inputs and controls maskable interrupt (IRQ) requests from peripherals.

All four of these LSI chips function simultaneously. Careful separation of their functions in the design phase has minimized conflicts between the chips. The only hardware level conflict between any two chips in the system occurs when ANTIC needs to use the address and data buses to fetch its display information. To do this, it halts the 6502 and takes control of the buses."

The USPTO granted U.S. Patent 4,314,236 to Atari on February 2, 1982 for an "Apparatus for producing a plurality of audio sound effects" - POKEY. Inventors listed: Steven T. Mayer, Ronald E. Milner

List of POKEs, which can be used as faster alternative to SOUND command in Atari BASIC! These SOUND registers are memory locations which control properties (tone, distortion and volume) of the ATARI's sound.

The even-numbered memory locations (53760, 62, 64, 66) control the TONE, i.e., which note the ATARI will play. This is identical to the second number in a SOUND statement. For example, to get the same tone as SOUND 0, 100, 10, 8 you would POKE 53760, 100. This specifies Voice 0, note 100. But what about distortion and volume? The odd-numbered memory locations (53761, 63, 65, 67) take care of these two characteristics for each voice via the following relation:

16*DISTORTION +VOLUME

where DISTORTION is the third number in the SOUND statement (10 in our example) and VOLUME is the fourth number.

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POKEY chip description retrieved from page maintained by Michael D. Current!
Some text excerpts taken from the book Best of Antic Volume 1 (article Some Sound Advice).