FM Algorithms

[Hexodus]

Question about FM algorithms in synths-

I understand that one oscillator modulates another, modulates another, etc etc...

But how?

Say you have just a basic sine wave. Adding another sine wave (or any other kind really) with no detuning and no crazy envelopes, produces an entirely different sound as opposed to the 2 playing un-modulated simultaneously. Basically, the tuning and level of one oscillator modulates the proceeding oscillator to generate a whole new sound. But how exactly is this happening? Because if you play the 2 together with NO algorithm (independent oscillators), that's all it is - 2 different sounds at the same time. Prolly a stupid question, just has me wondering. Thanks!

[jrisreal]

It's called frequency modulation aka fm synthesis...one operator modulates the pitch of another.

[symmetricalsounds]

use something like schope then play about and look at how having one oscillator on it's own looks, then start modulating that oscillator with another and see how that affects the waveform. that should go towards helping you to work it out.

[Hexodus]

good idea. i better try it

i understand the concept of FM, just not how one osc directly modulates another and so on...

[symmetricalsounds]

i found reading the theory of fm synthesis much more of a headfuck than actually using it. spending time with operaor made it all make sense.

[Ataxia]

I recommend looking up Brian Trifon (of Trifonic)'s YouTube videos. He explains FM synthesis in fairly good depth, FM8 in particular.

[bassinine]

http://www.soundonsound.com/sos/apr00/a ... ecrets.htm

[hifi]

don't know why everyone thinks fm is sooo complex. it's really NOT that hard to comphrehend

[Hexodus]

well, first of all - it IS that complex if you're new to it. can't expect ppl to just know everything man. you had to learn as well.

also, i didn't say 'how does fm work'. i asked how one osc modulates another as per their respective algorithm. bc that's a much different concept

[-[2]DAY_-]

i think the modulator introduces harmonics to the carrier wave by like magically smashing it into the carrier oscillator.. telling it to make little sinusoid bumps on the wave, which are spaced apart mathematically in some ratio that will scrape the speaker cones on those frequencies that the carrier and modulator waves' combined FM results.... err, hm. so if you FM a wave that's FMing another wave, it will make even more complex ratios of gritty bumps in the wave. I think modulating the pitch of the modulator will end up sending changing amounts of bumps into the carrier wave so it will morph the sound. .. etc etc. ad nauseum

you gotta do some heavier reading to learn the actual maths. i'm clearly clueless. :p

[1point5]

before getting caught up in complex FM algorithms, you need to fully understand how a basic 2 operator FM synth works.

There is one operator (oscillator) acting as a 'Carrier' and another acting as a 'Modulator'. The modulator is essentially applying vibrato to the carrier, causing the pitch to go up and down. When this is done at a high frequency it introduces new harmonics creating the rich sounds FM synthesis is capable of. Then by modulating the depth of the modulator (ie how far the pitch is being bent up and down) with envelopes and LFOs we can control the level of richness in the sound (ie prevalence of harmonics) and create natural decays and interesting modulation. The modulator and carriers' frequencies are usually played at a selectable ratio keep the same kind of sound with each note.

[Hexodus]

awesome. that makes a little more sense now. bc it's not simply 2 waveforms smashed together as that could get rather ugly. there is some sort of function that allows them to be harmonic to some extent and that's what id like to know. but your explanation helped clear that up a little.

onward with the investigation

[samurai]

I don't think that people find FM particularly difficult to comprehend. I just think that FM synthesis is harder to control than subtractive synthesis.

people have already explained it here and it's pretty easy to follow once you know what it is (one oscillator modulating the pitch of another). there's probably some complicated maths going on there which I'm sure somebody else can explain...

I think the main confusion with FM basically comes from the fact that the more oscillators you introduce and the fancier you make the algorithms, it makes it much harder to produce controllable results.

[hifi]

well, first of all - it IS that complex if you're new to it. can't expect ppl to just know everything man. you had to learn as well.

also, i didn't say 'how does fm work'. i asked how one osc modulates another as per their respective algorithm. bc that's a much different concept

wasn't talking about you. should have rephrased my statement. meant that most people on this forum think it is soooooooo complicated. it is pretty hard to grasp at first but not something that only a few people could comprehend.

also it ISN'T complex if you are new to it. it's just seems that way until you start using it then boom it's not so hard

[RandoRando]

i know how Fm works, but i honestly dont know it in depth. I just know if i have a harsh waveform with a high ratio as a modulator, my carrier is gonna get a nice sparkly timbre. Or a parabol or sine wave with a low low ratio as the modulator will give me a thick, hollow wood sound.