One channel no 16bit no 15kHz no sample no softsynth no bullshit POKEY bass (no, it has not been implemented in a tracker yet)
BotB Academy Bulletins
 
 
110695
Level 23 Chipist
post #110695 :: 2019.05.20 2:46pm :: edit 2019.05.20 2:47pm
  
  Slimeball, mootbooxle, ordinate, Savestate, b00daw and VinsCool liēkd this
Last weekend the #6 issue of Atari Fan
was released. I was looking forward to that mag, because there's been a thing that was teased for over a year - 23 page writeup on making one channel POKEY bass.

A lad going around as "Pavlos" compiled all of the useful info from the internet into one article, complete with explanations and tables.

I am currently in process of translating the entire thing. As it's quite long and in detail - and in conjunction with my sub-par tech knowledge - it'll take a while.

BUT FOR NOW I am able to give you the short version, which gives you "the meat" of the process.

"C" basses are sounds which belong to one of the four of the C distortion categories - C2. In this category you have three sounds available: T0, T1 and T2. The only frequency-independent sound is T1. It's only available on sampling track ST1.
In order to get stable (consistent) sound of the distortion C in C2 category while using div28 (64kHz = usual POKEY tuning) or phi2 (1.77MHz) you have to do one-time synchronization to sampling track ST1 and keep that track using only frequency dividers that are in the M3 set. If using 8-bit tunings you can use the divider table shown in table 18. In case of using div114 (15kHz) base clock there's no need to synchronize but you have to use channel 3. All dividers for div114 clock belong to set M3, and channel 3 has the ST1 track assigned by default.

Here
is the aforementioned "Table #18".
"M3 set" is explained within the article, but I haven't reached it as of now - not required in practice as the fitting dividers are listed in the table

As of writing I am not aware of any music software that makes use of this technique.

Hopefully some will appear soon : D hope yall have a nice day
 
 
110696
Level 4 Playa
Oli
post #110696 :: 2019.05.20 3:39pm :: edit 2019.05.20 6:41pm
  
  Slimeball liēkd this
Thank you for sharing this information, Zlew! There's a lot of new terms for me there, I gotta give a look to the POKEY's manual to catch up with what you just en-lighted us with!

This documentation seems to have relevant background for the terms and conventions that Pavlos used there:

http://krap.pl/mirrorz/atari/homepage.ntlworld.com/kryten_droid/Atari/800XL/atari_hw/pokey.htm
 
 
110844
Level 11 Mixist
post #110844 :: 2019.05.26 3:05pm
  
  Jangler and mootbooxle liēkd this
but zlew, just what is pokey bass??????
 
 
110850
Level 23 Chipist
post #110850 :: 2019.05.27 5:25am
  
  VinsCool and MiDoRi liēkd this
low frequency notes in general
 
 
110943
Level 28 Renderist
post #110943 :: 2019.05.30 6:16pm
  
  VinsCool liēkd this
I once tried to write a pokey sound driver in a long-forgotten age. I recall that only some register values gave some sort tonal sound, while most of them just played noise when I tried to make POKEY BASS.

I think only the register values where (n+1) was a multiple of three would give tonal sound. As far as I can see all the register values in table #18 conform to this rule.

I don't think I see anything new here so far. I think raster tracker already implements everything of this? I might have missed something though~ =w=

I have no idea what "sampling track 1" refers to actually. My closest guess would be AUDCTL1. It's not on the list of registers here:

https://en.wikipedia.org/wiki/POKEY#Registers

P.S.

fuckings to 16bit, 15kHz, samples, softsynths and SID
 
 
110948
Level 11 Chipist
post #110948 :: 2019.05.30 8:05pm
I love the random nature of Distortion C.
I always purposefully randomise the timbre from it hehe
 
 
110957
Level 23 Chipist
post #110957 :: 2019.05.31 12:45am
@Slimeball

ST1 is a fancy name for Channel 3 (out of 4)
 
 

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