Author Topic: C64 style arpeggio that changes over time  (Read 451 times)

Offline Domarius

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C64 style arpeggio that changes over time
« on: May 26, 2020, 07:39:25 »
Just wondering if there's a way to do this using traditional mod files, maybe the FM feature of the S3M format...

I love the way SID chip music can arpeggio but change the sound over time.  I think it's like setting up an FM instrument to go from muted to sharp as the note is held (like the wah sound of a trumpet) except you can do an arpeggio for the duration of the effect, rather than the note being triggered from the start each time the pitch changes in the arpeggio.

I uploaded a song I heard to show you what I mean, it's the arpeggio that's running from the start of the song, the way it gradually changes to a sharper sound.
https://youtu.be/QAvJVhA4LHU

Offline Saga Musix

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Re: C64 style arpeggio that changes over time
« Reply #1 on: May 26, 2020, 13:08:08 »
The typical sound you hear on the C64 is pulse-width modulation. The C64 synth is not using FM synthesis, but of course you can achieve similar effects with that.

You can do the same with samples (or FM instruments) in OpenMPT because an arpeggio does not retrigger the note. All you need is a sample which already has this pulse-width modulation "baked in". Many chiptunes do it that way.

Edit: In ProTracker MODs, there is another way to achieve this with a very small chip sample, by using the EFx (invert loop) effect, which modifies the sample data one frame at a time. See attached file for an example.
« Last Edit: May 26, 2020, 13:31:09 by Saga Musix »
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Offline Domarius

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Re: C64 style arpeggio that changes over time
« Reply #2 on: May 27, 2020, 01:30:08 »
Thanks Saga :) Now I know what to call it too (pulse-width modulation).  I get it now, I can just have a long sample that changes over time and the arpeggio effect will let the sample keep playing, it doesn't re-trigger the sample from the start like I thought.

The attached example sounds awesome in OpenMPT!  But doesn't seem to change over time in the two different media players I tried (Audacious and ZXTune) so I'm worried it won't carry across into whatever sound library is used to play it in a game engine (Eg. Unity, which uses FMOD).  It would be cool to do it like this, but I'm OK with the extra sample size if baking it in will work.
« Last Edit: May 27, 2020, 01:41:31 by Domarius »

Offline Saga Musix

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Re: C64 style arpeggio that changes over time
« Reply #3 on: May 27, 2020, 08:11:41 »
It definitely won't work in FMOD, I can tell you that. EFx is sadly not that well-supported. Audacious should support it though through the audacious-openmpt plugin. Is that not what it uses by default to play MODs?
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Offline Domarius

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Re: C64 style arpeggio that changes over time
« Reply #4 on: May 27, 2020, 23:47:32 »
I did some light reading on ProTracker's EFx and looks like it's quite controversial! Also the 2nd page I found seems to be you learning about it a decade ago! How cool is that? :)
https://www.un4seen.com/forum/?topic=7554.0
(Frames... now there's a technology I haven't seen in a long time... I had to get that URL from the page, not the address bar...)

Regarding Audacious, I'm using 4.0.3 on Linux, and looks like it uses ModPlug
https://i.imgur.com/wE6s1tB.png

I'd be interested to know if there is a specific list or collection of modules that use EFx, just to listen to them.  I collected the 3 off that page :)

Offline Saga Musix

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Re: C64 style arpeggio that changes over time
« Reply #5 on: May 28, 2020, 08:03:26 »
It's not an exhaustive list, but here are some good ones: https://modarchive.org/forums/index.php?topic=4131.0

For audacious, you should give this plugin a try: https://github.com/cspiegel/audacious-openmpt
I'm not sure if there are official binaries in some package managers for this plugin.
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Offline Domarius

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Re: C64 style arpeggio that changes over time
« Reply #6 on: May 29, 2020, 01:19:00 »
Thanks, I'll give it a go :)