self oscillation.then sweeping cutoff till you find note....Is it Beating ??

[nutrinoland]

On a synth...when resonance is turned all the way up into self oscillation and you sweep the cutoff till you match the pitch...something starts to happen to the sound as you are close on both sides of the note..and it changes the rate as u move around right next to it...what is this called ?
Is it called Beating ??
what is amplitude modulation then ?
Thanks

[Ruari]

Originally Posted by nutrinoland

what is amplitude modulation then ?

Amplitude Modulation

[nutrinoland]

haha..ya I looked at that first before posting here..but It was not so tempting to get into, with all that math...I find it a bit dry...
Maybe a simpler explanation would help...

so the resonance and sweeping cutoff...what is that ? Beating ?

[Ruari]

Yes, the maths can be a bit tedious sometimes.

In the simplest terms; imagine there is a little man controlling the fader of a single oscillator, he moves the fader in an up & down cycle (on, off, on ,off ad infinitum) as he increases the speed of the cycle eventually another audible frequency is generated.

Try it out yourself by turning the osc. balance hard left then use an LFO via the matrix to modulate the oscillator volume, then increase the speed of the LFO. Hear it?

That is basically how Ring Modulation works without having to trouble yourself with maths. Frequency Modulation is similar, but this time an LFO wouldn't be able to go fast enough so an audible oscillator is used to modulate another.

Here is an easy to understand guide to FM synthesis, start at the bottom & work your way up.

http://www.dubbhism.com/search/label/tao%20of%20fm

The "beating" you speak of, I'm not so sure. Let me play about a bit & get back to you.

[nutrinoland]

Thank You for the link . Its very helpful

[Timo]

'Beating' usually occurs when multiple waveforms clash (phase modulate each other) when summed.

Easiest example is set two oscillators to sine waves, mix them both at the same volume, and then simply increase the detune amount on one of the oscillators. You get amplitude modulation where the waveforms sum and cancel each other out.

http://infekted.org/virus/files/Timo/SineBeating.mp3

You can use it as an effect in its own right. As used in dubstep/grime.

http://infekted.org/virus/files/Timo/GrimeyMod.mp3

I used FM and detune for the above.

[Ruari]

Originally Posted by nutrinoland

Thank You for the link . Its very helpful

You're welcome

Timo's explained the "beating" for you, in my head I was thinking it was possibly a bit like phasing but I wasn't so sure.

[FSTZ]

I also acheived this with the frequency shifter

set the frequency shifter to about 50% mix and move the rate knob between 12 and 1 o'clock and you'll get that detuned beating effect

[nutrinoland]

Thanks Guys.
So Timo, If I have understood correctly, when two frequencies are very close together, they cause beating and Beating can be seen as a form of Amplitude Modulation.. ?
Is that correct ?
Is using an LFO on Amplitude the same ? will it achieve the same result ?

Would that mean that using LFO on pitch/OSC is like FM except that LFOs use frequencies lower than 20 Hz ? and FM uses audible frequencies as the modulator ?