When I write “building blocks” in the headline to this chapter, I don ́t mainly think of certain modules. Discussing certain modules will be the matter of chapter 5. I think of certain combinations of modules here, and only exceptionally of a certain module, and only when I want to show a rather uncommon way to use it. And a last note: I am not going to repeat things from the last 3 chapters. There are quite a lot of such typical and/or useful combinations of modules mentioned and described. So, let me talk about those, which went unmentioned (or mentioned only just by the way) so far.
I told about feeding back the end of an envelope to its trigger or gate input with certain modules in earlier chapters, and I am going to talk about special envelope modules in chapter 5. Let me talk about envelope-LFO combinations here and now.
There are 3 basic methods to combine an LFO and an envelope module to produce a more complex CV development. Two of these methods are exercisable with all envelope and LFO modules, the third one needs an envelope module, which offers modulation inputs for its individual stages.
Method 1: Envelope Modulates LFO
In its most basic form the patch looks like this:
The envelope modulates the LFO parameters, most commonly the LFO frequency or the pulse width (if the LFO ́s square/pulse output is used. With different settings for attack, decay, sustain and release (or more sophisticated parameters with specialised envelope modules) I get a couple of nice CV developments, and by changing the envelopes gate or trigger frequency there are quite a lot of different modulation shapes to gain.
Method 2: Envelope and LFO Add to Each Other
Here I mix the CV outputs of an envelope and an LFO and use the mixed (summed) signal to modulate things. With the mixer I can determine the share which each of this two modules shall have in the resulting CV development.
When the gate or trigger signal to start the envelope coming from an LFO I ́ll have two LFOs in this patch: the trigger/gate LFO and the LFO, which sends its output to the mixer (together with the envelope). But there are situations, when I want to use one and the same LFO as the trigger/gate source and as one of the two participants sending their outputs to the mixer. In these cases a clock divider comes in quite handy. The following two diagrams show the setup.We can modulate more than only volume VCAs of course. An interesting modulation target might e.g. be a VCA, which regulates the range of the pitch CV, that is sent to a quantizer.
Method 3: Modulating the Envelope ́s Stages
This method is exercisable only with envelope generators, which offer CV inputs per stage, so you might not be able to do so in your (hardware) setup.
There are some basic facts to remember when we modulate envelope stages. One of which is: if a stage has reached its end the next stage begins at once and without any further actions needed.
Of course, why mentioning that?
Well, modulating time related stages like attack, decay and release means shorten them sometimes and sometimes making them longer. But when I modulate e.g. the attack time by an LFO ́s triangle wave, it might well happen, that I shorten it so much, that it ends before the LFO has finished its cycle, or at least before another LFO cycle has begun. In this case I don ́t even recognise, that there is an LFO modulating attack, because the attack phase has (long) gone, and the decay phase has started, before the LFO could unfold its whole influence.
With only level related stages, like sustain we don ́t have this problem.
But we don ́t need LFOs to enrich envelope generated modulating CV. Combining envelopes is also a very nice idea to do, and again there are 3 basic methods, unfortunately only one of which can be exercised by whatever envelope module you have. The other two need at least and end- of-cycle trigger output.
Method 1: Adding Envelope Levels in a CV mixer
The graphic shows the principle. The output of the mixer delivers always the weighted sum of both envelopes. I say “weighted” sum, because I can – like always – determine the share of each envelope by adjusting different mixer channel levels.
But things are a bit more complicated. Do you remember: attack, decay and release are times! And after the adjusted time has gone by, the envelope jumps to the next stage. Therefore it might well happen, that one of the two envelopes has reached the decay stage, while the other is still in its attack stage. This means, that the overall level looks like the overall attack stage has two phases, whereas the envelope with the longer attack is still driving the level up, the envelope with the shorter attack is trying to drive it down, because it ́s already in its decay stage. What we see and hear is the sum of both.
And it is the same with the other time envelope stages. It might even happen, that one envelope has finished its cycle completely (= isn ́t sending any CV any more), whereas the other envelope is still in its release stage.
We can build up quite interesting envelopes this way, but to get a wanted certain one needs a bit of thinking at first.
Method 2: Chaining Envelopes
If our envelope generator offers an end-of-cycle trigger, we can chain one envelope after the other. In case we use a regular source of gate/trigger signals – e.g. an LFO – we have to take care, that the cycle length of this trigger/gate source is long enough to give both envelopes the chance to finish their work.
In a constellation like this the left envelope goes through its cycle – completely -, and after finishing its cycle it starts the right envelope, which then goes through its cycle – completely, if not interrupted by the next incoming end-of-cycle signal (in case the cycle of the left envelope is remarkably shorter than the cycle of the right envelope).
We have to consider the following cycle resp. frequency relations: the length of the cycle of the module, that initiates the whole chain, the lengthof the cycle of the left envelope, and the length of the cycle of the right envelope.
Method 3: Envelope Feedback
And now the real fun begins. A simple change makes the whole thing a fun LFO. I simply add a feedback patch cable from the end-of-cycle output of the right envelope to the trigger/gate input of the left one. Then I only need one single trigger impulse, and the whole patch never stops cycling through both envelopes – endlessly.
