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Synthpopalooza

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Synthpopalooza last won the day on February 18

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About Synthpopalooza

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    Male
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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, sadly, I can confirm that SKCTL=$0B is a great big nothing-burger. On real hardware, as well as Altirra > 3.20, it merely plays the associated note in both channels when equal, silence otherwise. Nothing to see here folks ...
  2. Most 7800 homebrews want the POKEY to be at $450 or $4000 so you may have to tweak that.
  3. It's that hi pass modulation. I've found a few other ways to get it too. One alternative setting, is to do a single 1.79 on the first channel. Play distortion 2 in the first channel and A in the third, and you can more finely tune the swirling effect. My next experiment perhaps
  4. Meanwhile, my latest, A.R.T.I. level 3 Settings AUDCTL=$64 (double hi-pass) 00 - $2x (swirly guitars) 01 - $Cx (gritty non mod bass aka RMT E) 02 - silent (modulation for 00) 03 - $Ax (accompaniment, standard square wave) This is a majestic Roman motif, with two distinct settings in the guitars. Swirling, and the tinny acoustic guitar which is created from using mod 31 frequencies in the third channel. arti-area3.asm arti-area3.s arti-area3.xex
  5. So a radical new discovery on two tone mode: If you don't set bit 8 ... SKCTL=$0B, the reset from channel 2 to channel 1 does not happen. This makes interesting effects The key here is to use a standard AUDCTL=$00, and play the same frequency in both channels, and set either A or C distortion in both channels. If you do ... the first channel gets set down an octave, while the second one stays normal, this makes an additive saw wave bass! In C distortion this is useful in the mod 3 or mod 5 frequencies. In addition, mod 3's in the first channel remain stable regardless of polycounters, and the waveform returned depends on even or odd frequency. If you bring the 1.79 clock into the mix, lots of wackiness ensues, especially in the 8 and 0 poly 9's. More experimentation is needed, but for now we instantly have two new useful settings with the double A and double C basses. The good news is both these settings will use the standard 8-bit A or C distortion tables (including a custom one I made for mod 5 frequencies). Will post a demo soon.
  6. My latest piece of music: The Egyptian level music for A.R.T.I. Settings are: AUDCTL=$51 (16-bit on first two channels, 15khz base clock) SKCTL=$03 (no two tone mode) 01 - $Cx (clarinet style lead) 02 - $Ax (harmonic for 01) 03 - $Cx (15 khz stable bass) 04 - $Ax (low square wave accompaniment) A few notes: This is a setting which was originally discovered by @analmux (RIP) back in 2009 and used in his Instrumentarium RMT module. @VinsCool was kind enough to get me a note table to play with. You set 16-bit with 1.79 mhz, and play distortion C on the first channel, using carefully selected frequencies, this makes a clarinet style timbre. Channel 2 can be left silent, or an $Ax distortion square wave can be played, which adds a harmonic that transposes the note down an octave. One disadvantage is that this setting suffers from the same drawback as the RMT C (mod 3) basses: Three timbres are output at random, depending on polycounter settings. The polycounter reset code developed by @pavros may mitigate this, especially if the 16-bit channel is played on channel 3. This setting also got used in the theme music for the recent Prince of Persia port. The $Cx bass is on channel 3. This allows for a stable bass of all the same waveform, unlike other channels which switch between two waveforms. This is possible since I am not using 1.79 on this channel. Sources, plus two binaries. The second one silences the harmonic, and I have included it as a comparison. I think the harmonic improves the sound. arti-area2.asm arti-area2.s arti-area2.xex arti-area2-a0.xex
  7. I've messed with 320D ... experimentally, but it was an experiment in interlace to try to get the equivalent of 320B with lower DMA costs. I still don't think it worked very well. What you could do in this case, is generate a 320B fontmap from this, then de-interlace it into two 320D maps. The idea is you combine a font swap with a color register cycle to make interlacing on vertical lines.
  8. OK, a comparison. I have side by side, a 64khz and a 15khz version of the same tune, using the two-tone pan flute setting. My thoughts are: The 15 khz version has the stable C bass, which goes lower, but there don't seem to be as many good fluttery notes as there are in the 64khz version. But in 64 khz, the bass has only range down to G#1. So I am torn which one I like better. What is everyone else's thoughts? I also tried a 15 khz version using the other timbre in $Cx, the smooth one ... but the selection of frequencies is severely restricted. so not an option it seems. arti-area1.asm arti-area1.s arti-area1.xex arti-area1-15a.asm arti-area1-15a.s arti-area1-15a.xex
  9. The thing is, because there's so much unexplored, POKEY's true potential has never been fully realized ... I've still got a few more jungles to explore yet.
  10. I have now documented the pan flute in 15 khz mode (AUDCTL=$41, 1.79 + 15khz, $2x distortion) Differences from 64 khz table: 1. The low end is still F#2 like the other one, but is slightly out of tune 2. F#5 is unavailable here and completely dropped from the note table 3. G#5 is the upper limit here, as opposed to A5 from the 64khz version. Otherwise this table is functionally the same as the 64khz table posted above, and therefore usable with the superior $Cx and $Ax basses in 15 khz mode. Yaay. Now to redo my ARTI music for 15khz, and compare the two. AUDCTL=$41 SKCTL=$8B AUDC1=$2x.txt
  11. Interlace Character Editor - my design. But it does full frame flicker, so not the best, unless you got one of those modern LCD TV's that does frame blending.
  12. Also ... the title music uses another POKEY feature called hi-pass filter. In this case, the first and third channels are used, set to a high frequency 1.79 clock, with the first channel set to the $Ax distortion. The third channel is silent, and modulates the first channel at such a high frequency that it creates a triangle-like waveform ... this is what I used to make the lead sound on the music. Most emulators, barring Altirra, can't handle it, it seems.
  13. Well, much of the sound effects in the game rely on using two-tone mode ... it's a function originally developed for cassette I/O on the 800/XL/XE platform, but I found a way to repurpose it for music and sound fx. In this case, the first two channels do the majority of the sound effects ... the de-rezz effects, all of the echoing effects, are all two-tone mode. I am actually not sure if any game releases, 5200 or XL/XE, have used this function before ... Basically, you store $8B into the SKCTL register, then play the sound fx on the first two channels, playing the first channel, while the second channel acts as a frequency carrier for the first. With the various distortions, and certain frequency settings, you get some of those echoing fx.
  14. Thanks for the kind words. It was fun doing the music and SFX on this. I tried to push the POKEY to do a few things it wasn't designed to do, with this.
  15. So, a techie question ... I don't really understand 100% the concept of two-tone mode, especially in the above usage. The patterns of the notes in the above table seem to be irregular. Best I can figure out is that the polycounter periods from the second channel cancel out the ones from the first, leaving a $2x wave and some noise. The first channel's frequency seems to correspond with the $2x distortion 1.79 note table. Does anybody have any ideas what's going on and how to predict it? It might help me alot when cataloging the 15khz version of this setting.
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