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Trance Forum Л Л Forum Production & Music Making - Can somebody please explain FM Synthesis in Detail?

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Can somebody please explain FM Synthesis in Detail?

john_c
IsraTrance Junior Member

Started Topics : 47
Posts : 263
Posted : Jan 27, 2005 19:10

Since I was using Reason for so many years, which has no FM synthesis in it, I have never learned what it is. I tried searching this forum with no luck. So can somebody please explain what FM synthesis is and how to use it? I think it has something to do with one Oscillator being the carrier for another one but thats about all I know. I know albino 2 and Z3ta+ can do it so please explain the theory behind it

Thanks synthwizards.

Spindrift
Spindrift

Started Topics : 33
Posts : 1560
Posted : Jan 27, 2005 19:22

Basically it's the possiblity to modulate the pitch of one oscillator with the audio signal from another oscillator.
Quite many synths have that possiblity and in that context it's quite easy to grasp.

Then you have proper FM synths like the DX7 where you have several oscillators that can be configured into various algorythms to be able to create a great variety of sounds.

Theoretically it might be possible to grasp how they work, but according to most people it's pretty much impossible to grasp how they work in a practical sense. I never really tried myself.
With synths like that it's pretty much pointless to even try to get to a state where you know exactly what you are doing, but just have to play around and experiment.

Try out NI's FM7 if you feel like having a go at proper FM synthesis.

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Yellow Warrior
IsraTrance Junior Member

Started Topics : 35
Posts : 898
Posted : Jan 27, 2005 19:41

Hi John_C,
I found this link from another thread.
Here this person has explained FM sysnthesis with reference to Yamaha DX7.

http://hem.passagen.se/tkolb/art/synth/dx7_e.htm

I hope it helped.

Enjoy.

Boom!

Rather than feeling that you're about to have the rug pulled from under you, let me teach you how to dance on a flying carpet

Hayez

Started Topics : 8
Posts : 393
Posted : Jan 27, 2005 22:44

Quote:

On 2005-01-27 19:10, john_c wrote:
Since I was using Reason for so many years, which has no FM synthesis in it, I have never learned what it is.

Subtractor has FM. there is also some good help in the manual.

john_c
IsraTrance Junior Member

Started Topics : 47
Posts : 263
Posted : Jan 27, 2005 23:40

thats the thing I dont get. What is "proper" or "true" FM synthesis then? I have FM7 and programming it looks hard to me. Not a big fan of the GUI honestly.

Surrender
IsraTrance Team

Started Topics : 506
Posts : 5388
Posted : Jan 27, 2005 23:57

i would like to know how to make those fm pulses like on the "natural born chillers" compilation - track 4- Jirah;s the very start of it.... rich pulsy fm's... i cant get that to happen.

"On the other hand, you have different fingers."
http://myspace.com/gadimon

Spindrift
Spindrift

Started Topics : 33
Posts : 1560
Posted : Jan 28, 2005 20:03

Ok, let me try again to explain.

Basically all normal subtractive synths have FM, ie Frequency Modulation.
Normally the source generating the frequency is limited to a LFO, ie Low Frequency Oscillator.

Of course by modulating the pitch of an oscillator with a LFO people would not associate the result with FM in any way.
To get that typical metallic ring in the sound you need a normal oscillator that can be used to modulate the frequency of another oscillator.,
Also in some rare cases a LFO that can go up to audible frequency.
That is of course possible with modular synths, or flexible synths like the Pro-One or MS-20.
The list of VA's that have that ability nowadays is quite long.

So...Frequency Modulation is by no means new, and was not invented by Yamaha.
What they did was to invent a completly new type of synthesis.

Away with the choice of waveforms and filters that make up subtractive synthesis.
Instead you have a set of sinewave oscillators that can be configured in different algorythms.

The oscillators acting as carriers would be then like the a regular sinewave oscillators, and the modulators like LFO's, but working in the audible range.
You can then connect those oscillators together in different configurations, or algorythms to make for example let a modulator be modulated by another modulator to achive more complex timbres.

By changing the frequency of the modulators you can then create overtones to shape the signal into saw or square waves and everything inbetween.
To add to the complexity, each oscillator have it's own envelopes to make it possible to change the timbre over time.

With a modular synth you could of course create true FM synthesis patches, provided you have enough oscillators and envelopes. Just as you could make an additive synthesizer by just mixing together sinewaves without any frequency modulation.

FM7 is quite easy to use compared to a DX7, thanks to the easy edit mode that emulates the controls on a subtractive synth.
Otherwise my approach to FM synthesis has always been to just play around like a blind man in the dark until it sounds good. But most of all...presets.

john_c
IsraTrance Junior Member

Started Topics : 47
Posts : 263
Posted : Jan 28, 2005 20:33

Thanks man that clears up a lot. Wouldnt Albino then be a true FM synth? Cause you can make OSC1 and OSC3 act as Operators or Carriers, where they don't actualyl produce a sound, only influence OSC2 and OSC4. Isnt this true FM then? Obviously you only have 2 possible operators compared to FM7's many more. Im just trying to imagine what these "bell" like sounds, sound like. Not typically a fan of bell noises and wondering if its worth me learning FM synthesis. Thanks.

Spindrift
Spindrift

Started Topics : 33
Posts : 1560
Posted : Jan 28, 2005 21:43

Well, the albino or z3+a is not pure FM synths because they are based on subtractive synthesis but have advanced modulation capabilities that make them capable of frequency modulation.

If you only use sinewaves and no filter you could make them preform very basic FM synthesis though.
Then as you say you would have a basic FM synth with very few carriers and modulators.
You can't chain them up to recreate what a synth like the DX7 does though.

FM synths is not only good for bell sounds of course, but have a quite distinct character. I can't say I'm a great fan of DX7 or the FM7, but they can be interesting to play around with if you feel limited with subtractive synthesis and can produce quite a varying arsenal of sounds.

Just check out presets on the FM7 and see if you find that it can produce sounds that you like and maybe try tweaking them with the easy edit mode.
Try a bit to change algorytms and pitch on the oscillators maybe, but personally I do not feel it's worth trying to get to understand what I'm doing really.

EYB
Noized

Started Topics : 111
Posts : 2849
Posted : Jan 29, 2005 05:48

FM rocks

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john_c
IsraTrance Junior Member

Started Topics : 47
Posts : 263
Posted : Jan 29, 2005 19:09

Btw guys, I found this. Very useful!
http://www.computermusic.co.uk/tutorial/fm/fm2.asp

Morax
Triac

Started Topics : 10
Posts : 348
Posted : Jan 30, 2005 19:39

well i didnt read all the replies, im sorry if anyone wrote the same before

Freqency modulation is when certain soundwave controls the freqency changes of other sound.

If the -amplitude value- of the "controller" sound will be at higher level ->
the -freqency- of the modulated sound will be higher.
and of course...
If the -amplitude value- of the "controller" sound will be at lower level ->
the -freqency- of the modulated sound will be lower.

see ya

Trance Forum Л Л Forum Production & Music Making - Can somebody please explain FM Synthesis in Detail?