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Complete POKEY note table for all distortion settings

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#1 Synthpopalooza OFFLINE  



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Posted Wed Sep 18, 2013 1:39 AM

When doing the music for Pac-Man Plus's Bentley Bear game, I noticed there was scant little documentation for the frequency settings for all of the possible distortions in POKEY.

I sat down at it, and compiled a note table that might be helpful to those using the POKEY for music. There is a text doc file, and an excel sheet which also shows the hex values.

Values are for these distortion settings:

Distortion 10 (AUDCx=$A0 - $AF) ... square wave, pure tones.
Distortion 2 (AUDCX=$20 - $2F) ... triangle wave, bell tones.
Distortion 12a (AUDCx=$C0 - $CF) ... sawtooth wave, buzzy tones
Distortion 12b (AUDCx=$c0 - $CF) ... sawtooth wave, non-buzzy tones

12b is different from 12a, in that you only use frequencies for AUDFx that are divisible by 3. This produces smoother tones than other frequency settings. The bass in Donkey Kong XM uses this method.

Settings are for 8-bit and 16-bit mode.

8-bit mode uses AUDCTL=$00
When using 8-bit mode, tuning errors will increase as you get into higher frequencies.

16-bit mode uses AUDCTL=$20 or $40 ... 1.79 mhz clock, with either channels 1+2, or 3+4 joined. When joining channels, the first AUDC register is zeroed, and the second is used to set the control and volume. the two AUDF registers use the 16-bit frequency value in a low-order and high-order format respectively. I used this method in the Bentley Bear game for the bass track in the title music, and the level complete music. On distortions 12a and 12b, tuning errors will also increase as you get into higher frequencies.

All of these settings were tuned by ear, using the distortion 10 table located here, as a reference:

I hope these prove useful. Enjoy! If anyone could double check my work, and proofread it, make sure it works ok, I'd appreciate it!

Attached File  pokey notes.xls   67.5KB   321 downloads
Attached File  pokey note table.txt   8.21KB   363 downloads

Edited by Synthpopalooza, Wed Sep 18, 2013 1:40 AM.

  • Trebor , PacManPlus , analmux and 4 others like this

#2 analmux OFFLINE  



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Posted Mon Jan 26, 2015 8:41 AM


[...] 16-bit mode uses AUDCTL=$20 or $40 [...]

Of course this should be AUDCTL=$50 or AUDCTL=$28.

#3 Synthpopalooza OFFLINE  



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  • Location:knoxville, TN

Posted Tue Jul 25, 2017 9:19 PM

I am updating this table soon with settings for 15kHz mode. This is an 8 bit setting that allows for higher octave notes in the above 4 distortion settings.
  • Trebor and kenjennings like this

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