LFOS AS ATTENUATORS/DC OFFSET GENERATORS
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Kirk was concerned that the following article might be “too technical or esoteric”.  I love a challenge as much as the next guy, so if this topic initially seems to fly above your head, don’t say he didn’t’ warn you….

But the truth is that the result Kirk gets from this programming technique results in another one of those “Holy Grail” effects that you never thought you’d be able to achieve!

Using the LFOs as Attenuators and DC Offset Generators

Part 1: A DC Voltage as a Modulator

By Kirk Slinkard

Has anybody ever told you that the ESQs or SQ-80 cannot control LFO frequency in real time? They told me that, and I took it as a dare. Here is another look at one of the "hidden" functions of the first Ensoniq synths that isn't mentioned in the owner's manuals.

Chart 1

1. FREQ=00
2. RESET=ON
3. WAV=SQR
4. L1=63
5. DELAY=00
 

Its Hip To Be Square

I'm sure some of us have noticed that if you take an LFO and set it like in Chart 1, you will end up with the equivalent of a constant DC voltage that can be used as a modulator.

Unlike the other LFO waveforms, the SQUARE wave has only a positive component. That way you can use it for trills that always start from your original note and go up in pitch by an adjustable amount. That's opposed to vibrato from a triangle wave that needs to go up and down in pitch equally. This Image portrays a visual representation of 
the modulator abuse presented in this article

RESET makes the SQUARE wave always start at the beginning of the waveform, at its maximum value, and it stays there forever since its FREQUENCY is literally zero.

This works a lot better than trying to use one of the ENVELOPEs for the same purpose, since the ENVELOPE will always return to zero, sooner or later, when you release the key.

A "DC OFFSET GENERATOR" is a function available on many modular synthesizers, usually with a knob to control the amount. It has a variety of uses that don't normally apply to prepackaged synthesizers like ours - but that doesn't mean they don't EVER apply.

How Low Can Your LFO Go?

The first demo patch here has OSCILLATOR 1 tuned all the way to it's lowest frequency, then the "DC voltage" from LFO2 is added to it to as a negative modulator to send it even lower. That actually puts it in the subsonic range - which means that we've just turned OSCILLATOR 1 into an LFO with all 32 waveforms available for the ESQs and all 70 with the SQ-80! And that's not including hidden waves.

Patch Name: WHLLFO

OSC1  -3, 00, 00, SINE, LFO2, -63, KBD2, -63
OSC2  -1, 00, 00, EL PNO, OFF, -, OFF, -
OSC3  -1, 00, 03, EL PNO, OFF, -, OFF, -

DCA1  -, OFF, -, -, -, -
DCA2  -, OFF, -, -, -, -
DCA3  50, ON, OFF, -, OFF, -

LFO1  (NOT USED)
LFO2  00, ON, OFF, SQR, 63, 00, -, LFO3
LFO3  00, ON, OFF, SQR, 63, 00, -, WHEEL

ENV1   (NOT USED)
ENV2   (NOT USED)
ENV3   +63, +35, -63, 40L, 00,  00, 14, 55, 63, 30

 

ENV4   +63, +63, +00, 39L, 00,  00, 06, 60, 06R, 37

FILT  000, 00, 43, ENV 3, +52, OFF, -

DCA4  08, 63, OFF, -

MODES OF, ON, OF, 00,  OF, OF, OF, OF

SPLIT/LAYER (NOT USED)


 We're using the SINE wave here, which is not available in the 3 regular LFOs. AM assigns it as a modulator to the amplitude of OSCILLATOR 2, giving tremolo that is always full strength. So OSCILLATOR 3 is set up with the same wave as 2, and can be mixed in to control the overall depth of the tremolo effect at DCO 3's LEVEL setting (try adjusting it).

You could put a MODPEDAL, VELOCITY, or some other modulation source here to control the depth of the tremolo effect in real time. So we've ended up with a patch where the MODWHEEL actually controls LFO frequency. In the normal WHEEL position it is very fast, and goes to a more musically usable speed as the WHEEL is moved all the way forward, as it tunes OSCILLATOR 1 even lower. This effect might not give you the ideal range of frequency adjustment, but this is only a proof-of-concept demo patch to show you one way to do it.

Don't forget that other modulators can be used on the LFO to change their amplitude. In this particular application, you can even increase the LFO's level by using it to modulate itself. And there's certainly no reason why you can't use other LFOs set up this way to modulate each other. In this patch you can see that we have the MODWHEEL modulating LFO3 which in turn modulates LFO2.

This brings us to our next subject...Continue to second
part of article

 

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