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  • Joined: 01 Feb 2014
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noise channel pitch in various trackers
Post Posted: Tue Apr 11, 2023 9:41 am
I've recently started experimenting with Furnace Tracker in the hope that it might replace Mod2PSG2 (great, but limited) and Sneventracker (less limited, but buggy and unfinished) as my go-to solutions for producing music.

I noticed that, unlike Mod2PSG2, Furnace actually lets you enter note values for the noise channel. I fully expected this to have no real effect or at least that only certain values work at all, but if I’m not imagining things, that doesn’t seem to be the case.

If I use channel 3 in white noise mode, but with the pitch being controlled by channel 2, I seem to be able to make out subtle differences in the sound. The general pitch stays the same, as it should, but attack and decay of the volume envelope seem to be slightly different depending on the "pitch" of the note in channel 3. The higher it is, the softer the attack seems to be.

Is that some sort of bug in Furnace or an actual feature of the PSG chip? In any case, which would be the correct value to put into channel 3 to get exactly the desired sound?
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  • Joined: 06 Mar 2022
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Post Posted: Tue Apr 11, 2023 9:48 am
Last time I used Furnace the mode for channel 2 driven noise actually required you to set the pitch values in channel 3, not channel 2 so the values you set in channel 3 should affect the sound and the values in channel 2 should not.

I'm sure I'm not explaining that very well, will attach some screenshots...
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Post Posted: Tue Apr 11, 2023 10:41 am
Here, so first screenshot is using the 3 preset noise frequencies. Only C, C# and D are valid, although Furnace kind of previews other notes when you first enter them, on playback it should only work with those 3 specific notes. You can use any octave though.

The second screenshot is using the square channel 2 frequencies, and here you can use any note but crucially you must enter it on the noise channel, NOT on the square 3 channel!. Quite what happens if you attempt to use square 3 at the same time I don't know, I suspect it's just ignored.

Apologies if you already knew that, I just found it very confusing myself.

Also, just a note - again apologies if you already knew this:
Kagesan wrote

If I use channel 3 in white noise mode, but with the pitch being controlled by channel 2, I seem to be able to make out subtle differences in the sound. The general pitch stays the same, as it should, but attack and decay of the volume envelope seem to be slightly different depending on the "pitch" of the note in channel 3. The higher it is, the softer the attack seems to be.

Usage of Furnace aside, that could be an expected behaviour of the PSG because changing the frequency alters the initial value in the LFSR but only when the noise channel is written to; so changing the note per square channel 2 wouldn't reset the sequence. See here and section on LSFR here.
presets.png (62.23 KB)
presets.png
ch2.png (71.76 KB)
ch2.png

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Post Posted: Tue Apr 11, 2023 11:16 am
willbritton wrote
Apologies if you already knew that, I just found it very confusing myself.


I did not! Thank you. So I just leave tone channel 2 empty if I set the pitch on the noise channel?
That’s much different from how other trackers handle it, but also much more convenient, as I don’t have to make separate instruments for pitch and volume envelopes.
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Post Posted: Mon Apr 17, 2023 7:51 am
I'm also trying to switch from Sneven tracker to Furnace and ran into the same issues.
I asked similar questions (like a week ago) on smspower Discord channel so you might wanna look that up.
Somebody even posted a small example file with the different noise types if you're interested.
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Post Posted: Tue Apr 18, 2023 1:09 pm
slogra wrote
I'm also trying to switch from Sneven tracker to Furnace and ran into the same issues.
I asked similar questions (like a week ago) on smspower Discord channel so you might wanna look that up.

I’m not on the Discord, not sure if I want to sign up. Do you know if that information is available elsewhere?

Furnace seems like a really good and powerful tool, but it’s peculiar in some ways and documentation is woefully sparse. I haven't found any information on whether it supports GG stereo for example.
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Post Posted: Tue Apr 18, 2023 2:23 pm
slogra wrote
I asked similar questions (like a week ago) on smspower Discord channel so you might wanna look that up.
Somebody even posted a small example file with the different noise types if you're interested.


It would be very kind if you could paste that part here too. Discord is not a very good place for preserving/sharing information.
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Post Posted: Sun May 14, 2023 8:52 am
I’ve got another question for the resident Furnace experts.

Maybe my understanding of how the PSG works is faulty, but I thought using channel 3 in periodic noise mode just plays the entered frequency four octaves lower due to using a 6.25 % duty cycle instead of the usual 50%. However, if I change the tempo of a song in Furnace (main tempo, not virtual tempo), that audibly affects the frequency of a note played on the noise channel, while notes played on any of the tone channels seem unaffected, as they should be.

What is going on there? And how do I have to treat a non-default tempo if I want to use the periodic noise as a bass that doesn’t sound out of tune?

EDIT: Nevermind. Apparently, I had to toggle the "Disable noise period change phase reset" option in File > Configure Chip to fix this. Sounds fine now.
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