PSYN-tology 6 [LFO Explained]

I'm going to deviate from the formula that I've been following in the earlier installments. In this one we'll stick to exploring the functions available in the Low-Frequency Oscillator [LFO] section. This'll be good grounding for some of the later tutorials, and I hope that it'll open up some fascinating possibilities. So let's start with a scratch patch (say, Bank H; Patch 000, if you haven't filled it already), and peel back the layers in the LFO.

So what's the difference between a regular oscillator and a low-frequency one? Usually nothing but the frequency range available, although some synths limit the waveforms, as well. Many ancient modular synths simply used one oscillator patch-corded into another oscillator, using the first as a control source. Modern synths may limit LFOs to less than 20 Hz.; barely into the range of audible frequencies. Above this, you get into what's commonly called Frequency Modulation (FM), but it's all the same thing with different results.

Which brings up my pet PSYN peeve: LFO 1 offer a range of 0 Hz. to 1000 Hz., as indicated by the Tooltips. LFO 2 & 3 show a range of 0 to 1.0 Hz. in decimal increments. Neither is correct, to my ears. Not only that, the descending reading (especially in LFO 1) differs from the Tooltip indication when raising the slider. Even though the Help file indicated 0 to 20 Hz., I'd guess (without comparative testing against a function generator) that both offer a range less than that, and I've learned to mentally divide by 50 or multiply by 20 to compensate. Makes it difficult to write a tutorial ...

Enough BS; you've got your scratch patch in, with Osc 1 sending a Sine wave. We'll leave this alone, except to crank the LFO knob in the Mod Sens section to full. Go to the LFO section and enable LFO 1, and raise the Destination Depth to 100%, so that we can hear what's going on. The first thing you see is the Set choices. The thing to remember here is that the F choices are free running; that is, the LFO will run constantly whether you're playing a note or not. The S selections are key-synced; they restart their phase ['cycle-shape'] with each MIDI note that you send it. The MONO selections have one modulation for all the notes; for example, all have the same vibrato. The POLY ones maintain a seperate waveform for each note; potentially a very full & complex sound. Leave it on FMONO for demonstration purposes, but don't neglect this setting in the future!

You're already familiar with the wave shapes, as they're the same as the oscillators, only much lower in frequency. When using L-FM and E-FM in the
Oscillator Mode, you're actually doing the same thing as we're doing here, only in the audio range. Leave the Sine wave clicked, raise the Depth to a few percent, and the Speed to (grrr!) 700 Hz. Set Destination 1 to Pitch. There's the classic vibrato sound. Raise the Delay slider to about 500 ms., and you'll get a nice fade-in for your vibrato. [Edit: Not really "fading in" ; more like waitinga half-second, then leaping in.] Reset the Delay to zero.

Set the waveform to Square and gradually raise the Depth to from about 10% to 100%. The sound ranges from a classic trill to alternating note a couple of octaves apart. Slow the Speed control down to (grrr!) 500 Hz. and switch between the two Sawtooth waves. The Inverted Saw produces an '80's Synth drum beat, and the standard Saw puts you in a mad scientist's laboratory. [You'll get similar results with the Sine and Triangle waves at this Speed.] Before we leave this area, click the Random waveform and experience my favorite mass confusion sound: the classic Sample & Hold sound. [It sounds great with the same wave controlling Cutoff Frequency and Resonance in a filter. Try it for 'extra credit'.]

Phase and Polar are a little difficult to explain without getting technical, so we'll slow down the Speed parameter to about (grrr!) 250 Hz. and set the wave back to Sawtooth. These two settings only work with the SMONO or SPOLY modes, so choose one and hit some notes, holding for a second or two. As you vary the Phase control, you'll hear the 'pitch sweep' start at a different point. Note that the Phase at 180 degrees with the Polar switch off seems to me to be the same as the Phase at 0 degrees with the Polar(ity) switch on. That would make sense.

In a similar vein is the Offset control and it's neighbor, the Keys knob. Let's get back to where we were before: FMONO, Sine, LFO Depth < 10%, Speed (grrr!) 700 Hz., Pitch as Dest1 and Modulation Depth to 100%. Offset adds a 'DC' voltage to the control signal. In effect, instead of your LFO (in this case, vibrato), being centered on the note you're playing, the Offset raises or lowers this center of variation for the LFO. This interacts with the Speed and Depth controls, so you can get quite a variation. Try some points between -100% and 100% to see what I mean. The Keys knob introduces a connection between your keyboard and the Speed control: key tracking. It's very similar to the keytracking available in the filters and the Keys switch in the oscillators. With a positive setting, the speed of the LFO increase as you ascend the keyboard. With a negative setting, the speed decreases as you play higher notes, and vice-versa. Neat performance tool; it was originally implemented in synths to emulate some orchestral instruments, but you need not be limited to that.

I sure you already have figured out the (Tempo) Sync options, but for the sake of completeness, here goes: Any setting other than Off disables the Speed control, allowing you to synchronize your LFO waves to PSYN's host tempo at short note increments up to several measures. This is an essential feature is almost any synth/effect these days, but don't overlook the possiblities of un-sync'ed LFOs. Sometimes there's a human quality imparted by varying from 'lock-step' perfection. Click it back to Off for now.

The Control section at the bottom offers you some expressive options. The Wheel, Aftertouch, and Breath knobs work in conjunction with the three Destination Depths to allow you almost any combination of static and variable LFO control. Say you want a little vibrato on all your played notes, but want to blast only some notes out with some very deep modulation. Back off the Destination Depth a little, and adjust your main settings to taste. Now dial in the Wheel knob, and use your KB Mod Wheel to have continuous control over those note that 'jump out". Aftertouch is great for those of us who are fortunate enough to have it, but it will choke a MIDI stream, and takes quite a bit of practice to master. It would be nice to be able to draw an automation envelope for an added level of control in Project5, but you can always reassign under MIDI Remote Control to bind to another MIDI message. How many of you have a wind controller or an old DX-7 breath control rig lying around? You can assign one of your controller knobs to CC #2 to control the Breath knob in a parallel fashion; it's just a different road to the same arrival point.

OK, we're down to the Modulation 'matrix'; possibly the most powerful area of PYSN, although it could be more flexible. [3 LFOs with 3 separate slots each for 15 destinations and 5 envelopes with 2 slots each for 15 destinations, and I'm ****in' about it! Some people are never satisfied!] I think were still at our vibrato settings, so increase the LFO Depth to 100% and switch the wave to Square. Change the Dest1 to Lev-All or Lev-01 any play a few classic tremolo sounds. This in conjunction with your Sync options can give the illusion of a pounding bassline while you add a drone, a pad & some lead lines over the top with the remaining oscillators. [Coming soon to a forum near you: Another tutorial ...] Change the waveform to the Inverted Saw to give a little 'decay' to the line or to Random to imitate my drummer on a good night. Switch the destination to PWM-01 with the Random wave enabled. Go back to Osc 1 any select the Square wave. Play a note while varying the Width control with your mouse to get a taste of what Pulse Width Modulation is all about. Of course, continue to experiment with the Destinations. Cutoff1 and Reso1 are active in this patch, and will yield some cool results that should be the jumping-off point for a ton of new presets.

Whew! Now multiply what we've just gone over by 2 more LFOs with three destination slots each, and the possibilities start to really open up. Each LFO can control 3 things, or can modulate the same destination in three different ways. See the Pitchin' LFOs patch for a sample of what you can do with pitch variations from 3 low-frequency oscillators. And we haven't considered the EGs yet. But that's for another day ...

Edited for clarity and accuracy.

Oy! "Night of the Living Tutorial". Where's all the graphics?
Someone delete that. Or use an Enter key on it.

And all with two fingers. Admirable. Crazy, but admirable.