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FM Synthesis


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I'm not sure who on here might or might not be intested but I posted this up on DOA earlier on in a thread about using native instruments FM8 synth, it was a bit long post so I though I might as well post it here incase anyone else might be interested...

 

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In the FM8 choose File->New Sound to get an initialised patch, this gives you a straight sine wave coming from operator F (If you look at the matrix you will see F is lit up and has a line down to the bottom line which is the output).

 

Next right click (I think) on E to activate it and route it to F, to do this click and drag up in the square which is below E and to the left of F. This means F's frequency will be modulated by E by the amount in that square.

 

F is now your carrier and E is your modulator and both are currently set sine waves playing at the same frequency.

 

You can now click on either E or F in the matrix page to bring up the page for each operator, here you can set the waveshape, pitch (ratio) and amplitude envelope (amongst other things). Leave both operators as sine waves (you can do alot with sines in FM) and have a play with the following:

 

1. The pitch of the carrier (F), if you change the ratio on operator F you will notice the pitch of the sound goes up and down just like you'd expect when changing the pitch of an oscillator on a subtractive synth.

 

2. The volume/evelope of the carrier (F), all the sound is come from operator F, E is only effecting the sound of F and cannot be heard by it's self. This means that the volume of F is the volume of the overall sound and that changing the envelope controlling it is much like the amplitude envelope on a subtractive synth.

 

3. The volume or amount of the modulator (E). Changing the amount the modulator is effecting the carrier adds more harmonics (there often seems to be a breaking point though where when you add too much is goes from a harmonic sound to a dissonant noise), therefore turning it down removes the harmonics. This means the amount (or volume) of the modulator is a bit like a filter cutoff, it sounds different and has different characteristics to a filter but it's similar. The evelope can be treated a bit like a filter envelope.

 

4) The pitch of the modulator (E), this doesn't change the pitch of the sound but it changes the harmonics created, this can be seen a bit like the waveshape setting of the oscillator. Changing the ratio by whole numbers results in harmonic sounds. Non whole numbers will get more noisy and dissonant as you move further away from a whole number. Much like with subtractive synthesis though slight detuning can phatten up a sound.

 

 

So have a good mess about with just those 2 operators with sine waves, see what you can do (I think you'll be surprised that it's actually quite a lot) and you'll start to get the basics down. Once you've have a good play try adding some different operators and using them to modulelate the carrier or other modulators or even both.

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