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About Synthpopalooza

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    knoxville, TN
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    Atari and Amiga computers, Doctor Who, science fiction, 1980's electronic and new wave music

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  1. So a few tips in this mode: For Case 1 (both tables) ... AUDF1 values where (freq+4) mod 15 = 0 will produce the basic frequencies, but as the value is stepped up by 15 each time, the sound gets slightly fuzzier and distorted. It's actually a cool effect, like putting $Cx distortion through a fuzz box. For AUDF1 where (freq+4) mod 5=0 but not mod 3 ... certain modulations on each note in the table will make the distorted guitar modulations. If the AUDF2 note comes from the non mod3 table, then the modulated frequency played is a 4th interval up from the root note. So more documentation is needed. But now that I know the pattern, it's easier to decode frequency settings.
  2. Sounds great ... Further documentation is needed for this setting, but I seem to have the frequencies sorted out in a manner that makes sense. Next step: sort out the $4x Reverse 16-bit setting @1.79 mhz. I have gotten thru 75% of the 65,536 settings now, then they need to be unscrambled and tuned.
  3. I can try to do up some non-RMT music if you like. I got a few ideas for mimicking that WSG Namco sound chip ...
  4. We're a long way from that .. but ... maybe something customizable that let's you import your own note tables and AUDCTL/SKCTL settings. There is a LOT left to document. And most of it is gonna be donkey work of stepping through 65,536 settings each time. 😳 As an example ... the above setting, I haven't even added the hi pass filter to it yet. It will eat three channels, but might even make things more interesting. There's a lot unexplored.
  5. OK, demo complete. This is a rendition of the Stickerbrush Symphony from Donkey Kong Country 2 Settings used: AUDCTL=$60 (1.79 mhz clock on 0 and 1) SKCTLS=$8B (Two tone modulation on 0 and 1) 0 - $4x (1.79 mhz, modulation) 1 - Silent (frequency carrier for 0) 2 - $Ax (standard square wave) 3 - $Cx (1.79 mhz, sawtooth wave, high lead) So, a host of explanations are in order ... When you set two-tone modulation on 0 and 1, with 0 as the $4x distortion, it creates a similar note table as $Cx ... you get a number of frequency tables, a couple of them are based on a mod 3 table, and a non mod 3 table, like in standard $Cx basses. When using mod3, you choose frequencies where (freq+4) mod 3 = 0. This makes for smooth bass tones. If you choose (freq+4) mod3 <>0 and <>5, rough bass tones are had. This is exactly like $Cx, but with different note tables. These are played on channel 1, the frequency carrier, which is always silenced. Now in channel 0, we do modulations. For mod 3 bass tones, we always do our modulations based on (mod+4) mod 5 = 0. This takes the frequency, and adds a bitwise modulation to it. Certain settings will morph the tone into a vibrato electric guitar. On settings where (mod+4) mod 5 =0 and (Mod+4) mod 3=0, you get the standard frequencies, but the higher you go in these, the fuzzier they sound ... which can be a desirable effect, like putting them through a fuzzbox that adds a slight distortion to the tones. The tune starts out with an electric guitar in the bass hit, then when the sequenced bass kicks in, it cycles through various modulations on the same note. I am attaching a rough note table, it is by no means complete, but is a very good beginning! Emulation notes: Prosystem and A7800, as expected, cannot do the two tone modulation correctly. In addition, Prosystem will play the $Cx channel correctly, but A7800 drops notes in that channel. Recording attached from Altirra emulator, which does this as it should sound on real hardware. Again, a test on real hardware will tell the true tale. dkc-stickerbrush.A78 dkc-stickerbrush.asm dkc-stickerbrush.bin dkc-stickerbrush-450.A78 dkc-stickerbrush-450.asm dkc-stickerbrush-450.bin dkc-stickerbrush.wav
  6. OK, a demo tune ... Took a bit of experimenting, but I came up with some modulations that make some good distorted guitars ... Setup: AUDCTL=$60 (1.79 mhz on 0 and 2) SKCTL=$8B (two tone mode) 0 - $4x (2-tone modulation) 1 - silent (frequency carrier for 0) 2 - $Ax (standard square wave, no modulation) 3 - $Cx (1.79 mhz, high lead) The tune is the stickerbrush symphony from Donkey Kong Country 2. The bass starts off with an electric guitar modulation, then when the bass starts, various modulations are cycled. The note table used is the Case 1, mod 3 bass table. More experimentation is needed, but this is a very promising start! dkc-briarpatch.asm dkc-briarpatch.s dkc-briarpatch.xex
  7. Demo song almost done ... New discoveries... some notes in the $4x SKCTLS mode have very good distorted guitar timbres! Very close to a note table on this ... Those who play Donkey Kong Country will know the tune ...
  8. I will work up a demo tune with this soon. Meanwhile, get TurboBASIC to run the programs to test it out.
  9. Documented another setting ... at least partially. AUDCTL=$40 (1.79 mhz on 0) SKCTLS=$8B (two tone mode) Channel 0 :$4x distortion, modulation of frequency for 1 Channel 1: Silent, frequency carrier for 0 This is a lot to go into here, but I made an extensive post here: We are dealing with which I call "$Cx distortion squared" ... three different cases, each one with two note tables. I haven't documented the third case yet, but I do have note tables, so the next step is demo tunes. In short, you get the same notes as in $Cx (both rough bass, and smooth mod 3 bass), but with additional modulation from the first channel ... which can be done in a mod 5, mod 3, or non mod fashion. Attaching a frequency table here. Also: AUDF1=11 and AUDF2=14 generates silence for note rests AUDCTL=$40 SKCTL=$8B AUDC1=$4x AUDC2=$00.txt
  10. More developments! This time, we are dealing with Channel 0 using $4x distortion, AUDCTL=$40, and two tone mode engaged! I have managed to decode frequency tables for two out of three possible settings. This is huge ... So some explanations are in order ... those of you who know how to us the $Cx distortion will remember, that you have three frequency cases to deal with: (freq+1) mod 3 = 0 and (freq+1) mod 5 <> 0 ... smooth bass tones, aka RMT bass C (freq+1) mod 5 = 0 ... either silence, or an intermittent smooth bass tone (freq+1) mod 3 <>0 and (freq+1) mod 5 <> 0 ... rough bass tones, aka RMT bass E The same thing happens with this setting, but multiplied... and we have three possible cases here. For purposes of this post and the attached document, the following terminology is used: AUDC1 and AUDC2: Distortion settings of channel 0 and 1 AUDF1 and AUDF2: Frequency settings of channel 0 and 1 Set AUDC1=$4x, AUDC2=$00, AUDCTL=$40 (turns on 1.79 mhz for 0) and SKCTL=$8B (two tone mode) Case 1: AUDF1 where (freq+4) mod 5 = 0 This is a fairly easy setting, very similar to $Cx distortion. Two tables are here for AUDF2, one with a mod3 bass setting, and one without (with rough bass tones). By stepping AUDF1 through multiples of 5, modulations are introduced into the note played! This can be used to make a PWM or sample and hold type random timbre, or other interesting effects. The mod 3 bass behaves just like RMT C, random timbres are played depending on system timers. I have made a note table for this setting, but it differs from RMT C. For the second table, we use non mod 3 values, like RMT E. Also: Where AUDF1 has (freq+4) mod 15=0, those settings are exactly identical, and may be considered to be your base setting in this case. Case 2: AUDF1= (freq+4) mod3=0 and (freq+4) mod 5 <>0 This makes some interesting results. We have smooth bass tones, but they are interspersed into two tables for AUDF2, with an octave difference. By altering AUDF1 by multiples of 3, modulations are introduced into the notes played in the second channel. Case 3: AUDF1= (freq +4) mod 3<>0 and (freq+4) mod 5 <>0 Undocumented as of yet, but there are a lot of strange frequencies, some noises, and some vibrato distorted guitars, on the order of the previous $4x setting I was playing around with. I am attaching a document, and three Turbo BASIC programs: FTEST48B.TUR ... steps through all 65,536 settings, and lets you compare them to a standard $Ax square table on channel 2 F48BMOD3.TUR ... steps AUDF1 through multiples of 3 F48BMOD5.TUR ... steps AUDF1 through multiples of 5 These controls: + or - ... changes the $Ax channel through the standard values (C3 to C4) up and down arrow: changes AUDF1 left and right arrow: changes AUDF0 Now, let's get this modded for RMT. One more bit of info ... AUDF1=11 and AUDF2=14 generates silence for note rests F48BMOD3.TUR F48BMOD5.TUR FTEST48B.TUR AUDCTL=$40 SKCTL=$8B AUDC1=$4x AUDC2=$00.txt
  11. My thing is ... looking to see if I can piggyback second POKEY on top of the existing one in the XM. The thought of either stereo POKEY or 4 16-bit channels makes me drool... lol
  12. It can ... however this is what I want to do ... POKEY settings as follows: AUDCTL=$04 (HI pass filter on 0, from 2) SKCTLS=$8B 0 - $Ax square 1 - silent (two tone modulation of 0) 2 - silent (hi pass modulation of 0) This burns 3 pokey channels, but gets you double modulation. SID type sounds ... plus you got one other POKEY, 2 TIA, and 8 yamaha channels left. 😁 You can also do two 16-bit pokey channels, and have perfect note resolution in any distortion setting. This would be an NES slayer.
  13. Halfway done. I have half of the 65,536 settings documented for the $4x Reverse 16 setting. I have a rudimentary table ... note, these are not grouped by octave number, that will come later, but you can get from about c1 up to about c3 so far. Here's how it works: Put $50 in AUDCTL, silence the second channel, set first channel to $4x. Turns on 16-bit and sets first channel to1.79 mhz. There is some sort of averaging which goes on between the bit counters in the first two channels due to $4x bit counting, which creates the warbling guitar effects in the first channel. The tunings in some of these may be off ... I did them by ear. Also, the table is half done. I still need to get the settings where AUDF1 (2nd channel) > 128. Next, I will do up a frequency table, and sort these out by tuning, until finally we get a note table. Emkay: It'll be on you then ... hack this baby into RMT. Also, anyone who wants to dig into this, and make a tuned table out of what I got ... feel free! This is going to make some wicked guitars ... I am also going to experiment with the other clocks (64 khz, 15 khz) and see what happens as well. So far tho I think 1.79 mhz is the best bet. Then ... modulating this stuff with a hi pass filter on channel 3. AUDCTL=$50, AUDC0=$4x.txt
  14. Reviving this topic ... I am spending my quarantine time doing a frequency table for $4x distortion, 1.79 mhz, and reverse 16-bit mode (0 plays, 1 is silent). about 25% done. Going to need some help tuning it tho. This one produces warbling electric guitars, and the frequency value in the 2nd channel increases the vibrato. This is going to be cool when it's ready.
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