How do tremolo effects really work?

deefstes

I don't have a tremolo pedal yet but can imagine that it might be one of the first effect pedals I'd be interested in getting. I'd like to understand something about it though and I'm hoping you guys can shed some light.

The only tremolo effects I've used so far have been the tremolo effect on my Roland Cube 80X amp (of which the depth can not be adjusted) and some tremolo VSTs on REAPER. There is a crucial shortcoming with the tremolo VSTs I've used so far which I really hope will not exist in tremolo pedals but I'm not sure exactly how they work. Let me explain.

The way I assume the effect works is to generate a modulation waveform which is applied to the input signal. Let's work with a sine modulation waveform with a fairly heavy depth (90%). Here I've made a drawing of the modulation envelope (blue) and two notes being played (red). You'll notice the notes have a very sharp attack and a gradual decay (sort of like a guitar note).

So when the modulation wave is applied to the input signal, this is what we get:

So far so good, but what if the second note happens to coincide with a trough of the modulation wave, like so:

When the modulation wave is applied to this input signal, we get the following. Notice how the attack of the note is pretty much lost. It results in a very different sounding note to the first one.

So, is this how tremolo effects generally work (it does seem to be the case with the tremolo VSTs I've tried)? Or are there VSTs (and pedals) that have some sort of functionality not to modulate the attack part of the note? I'm not sure how that would work though?

deefstes

I might add that this is only really a problem when you use a deep depth of tremolo effect. I've never noticed it on my Roland Cube due to the depth being fairly limited (or perhaps because the Roland Cube does it differently from the method described above).

But the way I understand it, an unodulated signal with a low depth envelope like this:

...would result in a modulated signal like this:

It can be seen here that the second note doesn't differ all that much from the first note. Notably, it still has a fairly prominent attack.

ezietsman

You are correct yes. If you happen to play a note when the tremolo modulation is in a trough, the attack is lost or dampened. Tremolo effects do not take into account when you play, its an oscillator that modulates your signal at a constant rate from the time you switch it on.

deefstes

ez wrote: You are correct yes. If you happen to play a note when the tremolo modulation is in a trough, the attack is lost or dampened. Tremolo effects do not take into account when you play, its an oscillator that modulates your signal at a constant rate from the time you switch it on.

Bummer :'(

ezietsman

deefstes wrote:
ez wrote: You are correct yes. If you happen to play a note when the tremolo modulation is in a trough, the attack is lost or dampened. Tremolo effects do not take into account when you play, its an oscillator that modulates your signal at a constant rate from the time you switch it on.
Bummer :'(

Of course, the trick with them is to have the tremolo speed set match song's tempo and play in time, not necessarily a plug in and be awesome effect ?

AlanRatcliffe

[EDIT] Bit late with some things here - I'm typing slowly this morning, and about three threads at a time. LOL!

So, is this how tremolo effects generally work

That about sums it up.

Some designs use a triangular or saw waveform though. Some even use a squarewave or are switchable.

Notice how the attack of the note is pretty much lost. It results in a very different sounding note to the first one.

Hence the need for the player to play in time with the tremolo when using slower speeds and higher depth... ?

Or are there VSTs (and pedals) that have some sort of functionality not to modulate the attack part of the note? I'm not sure how that would work though?

An envelope follower can be used for all kinds of things.

Take a look at what Cusack and Red Witch are doing with some of their pedals. Of course you can replace your LFO with a step sequencer and really go to town (take a Look at the Roger Linn stuff and have your mind blown).

BTW - NI Guitar Rig lets you test out using modifiers like LFOs, envelope followers, step sequencers, etc. to control any parameter of any effect (or multiple parameters at once - it even lets you reverse the phase, so you can have things like two phasers auto panning in different directions, but controlled from the same modifier - all great fun!). That - and the parallel chain capability - is why GR is far better than any other amp/FX sim.