about the algorithms...

Ask anything your want about Megadrive/Genesis programming.

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papertib
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about the algorithms...

Post by papertib »

Hello everyone, I'm new here and I have a question :D
I'm trying to make music with Shiru's VGM Music Maker but I can't understand how the algorithms work and I wasn't able to find concrete informations about them. Could someone explain me the logic behind the algorithms and how they affect the sound?
superjoebob
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Post by superjoebob »

I have a feeling that the answer to your question is going to be fairly complicated and technical :shock: . I don't know exactly how FM works, I do know there's an outline of what the operators are particularly good for on SMS Power though: http://www.smspower.org/maxim/Documents/YM2612 (Scroll down to "Page 6")
I think it's taken out of the original 2612 docs.

Generally what I do is I come up with a sound, click around to see how the algorithms change it, then pick the algorithm that changes it the most and toggle things to see what I can turn it into. FM is hard eh
On a never ending quest to compose for the Genesis/Megadrive
GManiac
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Post by GManiac »

To understand background on algorithms, you may read translated Japanese doc from the first post
viewtopic.php?t=386
Direct link
http://nemesis.hacking-cult.org/MegaDri ... slated.PDF

First, you must understand what is operator, than you should understand algorithms.
Briefly, operator is sine generator with input phase adder. Output of another operator can be scaled by some value and then added to input phase of first operator.
For example, real values for YM2612:
2*pi = 1024.
2*pi is 360 degrees, full phase cycle.
Operator's output lies in limit -8168..+8168, that is almost -16*pi..+16*pi
But scale factor is 1/2, so one operator can modulate other one only by values from -4084 to +4084, or -8*pi to +8*pi. But there is algorithm where one operator is modulated by output of TWO other operators, and yes, their output is added first, and only then it's scaled by 1/2 and added to input phase of modulated operator.

To get practical experience of algorithms you need something else. In articles on FM synthesis I saw short descriptions of practical uses of various effects: detune and so on. But I don't remember if there was any info on using algos.
papertib
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Post by papertib »

Wow thanks, I didn't get everything but at least I have a better understanding of the operators.
The links were really useful, I'll have to make some tries with the algorithms and that should do it :)
Thanks for the help, you two!
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