Introduction to MIDI and Computer Music: Assignment 3, Part 2
DO THIS: Begin with an Init Patch for SubTractor. (Click on SubTractor, then choose Edit > Reset Device.)
You can hear a very clear example of this technique near the end of Emerson, Lake, and Palmer’s song, “Lucky Man,” played on a Moog modular system in 1970.
You make a SubTractor patch monophonic by reducing its Polyphony to 1. If you want overlapped notes to run together smoothly, then use Legato mode, rather than Retrig mode.
Retrigger mode is the default; it restarts the envelopes every time you play a note. Legato mode restarts envelopes only when there is a gap between the release of one note and the attack of the next. If there is not a gap, then the pitch changes when you play a different note, but the envelopes continue their progress as if you were still holding down the first note.
To make the pitch slide from one note to the next, use the Portamento knob to increase the amount of time it takes to slide.
DO THIS: Your patch should be monophonic, with legato mode engaged and a non-zero portamento time.
Normally, the outputs of the two SubTractor oscillators are added (or mixed) together. If you tick the Ring Mod box, and turn the oscillator Mix knob all the way to the right, you get ring modulation.
To make this work, the pitches of the two oscillators must be different. Play around with different waveforms and tunings for the two oscillators. Make sure that Osc 2 is turned on!
DO THIS: Your patch should use ring modulation, with the two oscillator pitches tuned differently and using whatever waveforms you like. Don’t forget to turn on Osc 2 and turn the Mix knob all the way to the right!
To set up any kind of modulation, you use a control source called an LFO, or Low Frequency Oscillator. This works like any other oscillator, except that the waveform it generates oscillates relatively slowly, at a sub-audio frequency — that is, a frequency below the lowest frequency that humans normally can hear (about 20 Hz). You don’t listen to the LFO output directly; instead you use it to vary some other aspect of the sound that you can hear, such as the pitch, amplitude, or filter cutoff.
Let’s say we want to add vibrato to our SubTractor patch. Use LFO 1 as a control source, and choose as a destination one or both of the audio-rate (i.e., audible) oscillators. Do this by pressing the Dest (destination) button in the LFO 1 panel so that Osc 1,2 lights up.
You have to turn up the Amount knob to hear any change to the oscillator pitch. This knob controls the depth of modulation — in this case, how much the LFO pushes the frequency of an audio-rate oscillator above and below its offset. The greater the modulation depth, the wider the vibrato. Use the Rate knob to adjust the LFO frequency — the speed of the vibrato. Choose an LFO Waveform. The bottom two waveforms (the ones represented by squiggly lines) are random, rather than strictly periodic. Experiment!
Use the modulation wheel for its original purpose: to control the depth of modulation. In Part 1 of this assignment, you used the mod. wheel to control the filter cutoff frequency. To make it control the LFO instead, turn up the LFO1 knob next to the mod. wheel.
For this assignment, please set the F. Freq knob to its center position, so as to keep the mod. wheel from affecting the filter cutoff frequency.
The Amount knob in the LFO 1 section functions as an offset, and the modulation wheel changes the LFO depth relative to this offset. To have vibrato only when you raise the mod. wheel, turn the Amount knob all the way down (a depth offset of zero).
DO THIS: Your patch should use an LFO to modulate the frequencies of both oscillators. Select any waveform type and any rate for the LFO. Use the modulation wheel to control the modulation depth, so that when the wheel is all the way down, there is no vibrato.
NOTE: Some people use the word modulation in a broader way to refer to changes you make to a parameter using any type of control source, not just a cyclical source like an LFO. That’s why SubTractor has a Mod Envelope: an envelope you can use to modulate something else.
For more detail about SubTractor, choose Help > Reason Help, and look for the “SubTractor Synthesizer” topic in the list at the left of the window.
The best way to learn SubTractor programming is to study the example patches in conjunction with the manual.
Go to the next part of the assignment.