Pulse-width modulation (PWM) - Modular V Tutorial

[Descending Electronic Tones] - So far, we've just used our Low Frequency Oscillator, LFO, to control the cutoff frequency of our filters. However, there is lots of other places we could patch an LFO into on our modular, and a really useful one is the pulse width modulation. That will change the character of the sound following the speed of the LFO. Let me choose Template, Template Square Wave initially. [Low Electronic Tone] There's our lovely little square wave shape. And if you remember, the pulse width control on the driver, or bank of oscillators, affects how wide that pause and go impulse is. [Low Electronic Tone] Changing the pulse width changes the character of the sound. But rather than sitting here and doing this manually, let's call in our LFO to do that for us automatically. I'm going to patch from the triangle output of the LFO, something that rises and falls steadily without a sudden jump, such as the sawtooth or square wave has. Patch that to pulse with modulation, increase its pulse with the maximum to change its shape to be a pure triangle. And change this to not follow MIDI but instead be under manual control here and set it to and intermediate frequency. I'll play a note and start increasing the modulation depth, how strongly the LFO is controlling this pulse width. [Tonal Ascending Electronic Sound] Hear the increase or almost a sort of coursing or Doppler type of sound. [Tonal Ascending Electronic Sound] I can make it very subtle, as if two oscillators are de-tuned. Or very fast nervous, [Higher Pitched Tonal Electronic Sound] That's a great way of creating a high tension sound, by the way. Indeed, it's even more fun when I bring in a second square wave. I'm going to re-patch this down to my mixer, connect my mixer, back to my filter, cramp another oscillator in this bank. That means that oscillator is also controlled by this pulse width control for the driver. Connect it down to my mixer, enable it, drop it down an octave. [Electronic Keyboard Tones] Coming at a very fast modulation increase, a really high tension, nervous sound. [High Pitched Electronic Keyboard Tones] Or I can make it more subtle by dropping down to a lower frequency. [Lower Toned Electronic Keyboard Sounds] And decreasing its width by clicking on this little radar pattern next to the jack to change the modulation depth. [Electronic Keyboard Sounds Ascending In Volume] [Lower Toned Electronic Keyboard Sound] Now why did I use a triangle wave instead of something like a sawtooth or a square wave? Well, a sudden jump in modulation results in a sudden jump in tone, which may or may not be what you want. For example, I'm going to pull the sawtooth wave over, connect it to the pulse width input instead, change the pulse width on the LFO, back down to zero so I have a normal sawtooth that is base frequency. And you can hear things jump as the sawtooth resets. [Skipping Electronic Tones] Now maybe you want that sort of hard resetting sound or it might just be annoying. I mean if you're trying to go for that sort of sound, holding the square wave and have a lot of fun with this. [Ascending And Skipping Electronic Tones] You could even change the pulse width so it cuts out temporarily. [Ascending And Skipping Electronic Tones] You can also invert the modulation depth so instead I go to a minimum pulse width, dropping out the sound. [Skipping Electronic Tones] There we go. Sometimes just backing off a little bit can make a sound a lot more musically useful. Now this sounds like a whole bunch of oscillators de-tuned rather than just two. So pulse width modulation is certainly a way of creating a thicker, more coarse sound when you only have a couple of oscillators available.