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Hi everyone, I am new to synthesizers. I have a few questions I was wondering if anyone could answer,
What is modulation?
What does it do?
What is an example of it?
I'm a little confused at how some sites have defined them.

ph.billy wrote:Hi everyone, I am new to synthesizers. I have a few questions I was wondering if anyone could answer,
What is modulation?
What does it do?
What is an example of it?
I'm a little confused at how some sites have defined them.

Hi Billy

modulation in this case is applying an additional signal ( like another wave, a manual controller, keyboard pressure, etc.) to a sound to change its characteristic in its pitch, spectrum, amplitude, etc. When a guitar player bends the string up and down, he modulates the pitch creating a vibrato effect while a harmonica player could modulate the volume and spectrum covering it with his hands.

Modulation is one of the key components of a synthesizer, because without them the sound would be very simple and monotonous (don't confuse with monophonic!)

Typical modulator sources of a synth are or could be: the envelope generators (EG), low frequency oscillators (LFO), key velocity and aftertouch, mod(ulator) sequencers, and all the wheels, joysticks, slider and pots you will find on every synth.

Typical modulator targets are the pitch, amplitude, frequency response (applied filter), waveform, panorama, etc. of an oscillator.

The best example is your own voice: since your vocal chords only oscillate with a pitch you decide or control (modulate) yourself, your vocal cavity (tongue, lips, etc.) changes the tonal characteristic to words or sounds. All these movements are modulators applied to the sound of your vocal chords which here have the same function as the oscillator in a synth. Without modulation, the sound would always be the same.

Instead of the word modulate, think of the word control. For the word modulator, think controller. For the word modulating, think controlling.

In its simplest terms, modulation is using something 'to control' something else.

Such as using how hard a key is hit (velocity) to control the loudness (amplitude) of the sound.

Or using how much you push a joystick to the right, to control the pitch of a note.

Or using a slowly evolving signal (envelope) to control the tone (filter) of a sound over time.

Or using a cyclic signal (LFO) to control pitch and create vibrato.

To modulate something you usually have to specify three things:

The source (the controller).
The destination (what you want to affect).
The amount, or intensity, you want the source to affect the destination.

Such as:
Source: Velocity
Destination: Amplifier Envelope
Amount: +127

Or...
Source: Joystick +X
Destination: Pitch
Amount: +2 semitones

Or...
Source: Envelope
Destination: Filter cutoff
Amount: +64

Or...
Source: LFO
Destination: Pitch
Amount: +3

etc.

Modulators (controllers) don't generate sound themselves. They just generate invisible, inaudible signals that are used to control the sound in some way, effectively to make something happen, by an amount of your choosing. In other words, they tell the sound engine what to do.

Very similar to MIDI. Midi controllers don't generate sound, but they control the engine that DOES create the sound, and tell it what to do.

As axxim mentioned there are loads of different types of 'controllers', and they each create signals in different ways. Velocity, aftertouch, LFOs, Envelopes, pitch wheel, mod wheel, etc. These can all be used to affect or control something else.

I waited to see how someone else would answer ph.billy's question. Your explanation is great axxim but I'd like to get more longwinded with this topic.

Modulation occurs when any part of the synthesizer changes another. So you may have one oscillator modulate the pitch of another (cross modulation) or the volume of another oscillator (ring modulation). You may modulate the cutoff point of a filter with an envelope (filter modulation) and countless other examples. The point is that in every case one module of the synthesizer changes another in some way. Thus 'modulation' is a general term.

In synthesis, to "modulate" is a verb that means "to vary over time". It is not to be confused with "modify" which is static. A waveshaper, filter, or drive circuit are good examples of modifiers as opposed to a modulators because they do not vary other parameters within the synth over time, they only act upon signals that are fed to them.

Getting into more detail about controllers, sources, and modifiers will only get confusing. Timo's insight on thinking of modulators as controllers is wonderfully illustrated but may become hard to understand when considering audio sources as controllers (FM) or controllers as audio sources in the case of audible rate LFO's. Not to mention modifiers as sources in the case of self oscillating resonant filters and other "rule breakers". But if you can ingest the information provided in this thread you should have a decent grasp on things. Don't be afraid to ask questions.

CharlesFerraro wrote:In synthesis, to "modulate" is a verb that means "to vary over time".

Damn, aren't we a helpful bunch! Good to see everyone go deep into helping. The above is probably the easiest way to think about "modulation" if you don't wanna get scared away with technical jargon. Knowing this, it'll help to review all the answers provided while you learn to assign variables to affect other ones to pad your experience with knowledge. If you've got any questions about implimenting this in Radias/R3, leave them and we can help you out.

Thank you everyone. That makes a lot more sense