The EM Poll

Pushing the Envelope

Jan 1, 2006 12:00 PM, By Len Sasso

           

Envelope” is not a four-letter word. If you've been limiting yourself to simple ADSR envelopes in your synth programming, you're missing out. A variety of synths and samplers now offer breakpoint envelopes with flexible routing and shaping options. In this article, I'll discuss how to creatively use breakpoint envelopes as a sound-design tool. For my examples, I used Native Instruments Absynth 3 soft synth, which has one of the most powerful breakpoint envelope implementations available. But you can use most of these techniques in other synths, including earlier versions of Absynth.

Breakpoint envelopes differ in two ways from the fixed-stage envelopes found in vintage synths: they have more stages, and they give you more control over the parameters for each stage. In the case of Absynth 3, the envelopes can have as many as 68 stages, and you have control of each breakpoint's time and level, as well as the shape of the curve (called the slope) between it and the previous breakpoint. Furthermore, the envelopes have two forms of MIDI control, five modes of operation, and integrated LFOs.

FIG. 1: Breakpoint envelopes (from top to bottom) control channel one Main and Mod oscillator pitches, lowpass filter cutoff and resonance, channel two filter cutoff, and channel three volume.

A Pitch in Time

I'll start with a basic 2-oscillator patch and use breakpoint envelopes to evolve it into a 5-voice song that is played by holding a single note. Instead of triggering individual notes as you would with a step sequencer, breakpoint envelopes are used to create volume pulses. Other breakpoint envelopes, applied this time to each oscillator's tuning, control pitch. Finally, I'll use Absynth's looping, retriggering, and LFO envelope modes to add interest to the sequence. You'll find audio examples and an Absynth 3 patch bank containing all the patches in Web Clips 1 and 2 on www.emusician.com.

Start with the Ab-synth default patch and activate the oscillator in channel one (Oscil 1), set its mode to Double, and tune the second oscillator (labeled Mod) an octave higher. You can use any waveforms and Balance setting for the oscillators; I've chosen sawtooth and triangle waveforms for the Main and Mod oscillators, respectively, and set the Balance to 0.60.

Next, go to Absynth's Envelope window, select the Oscil 1 Amp envelope, and select Generate A/R Pulse from the Transform menu. Keep the default settings, which will generate eight eighth-note pulses. Each time you play a note, you'll now hear eight pulses. Set the envelope to Loop mode, and adjust the level and the slope of some of the 0 dB breakpoints, which are located at the top, to create a repeating, accented pattern.

Ensure that Absynth's Envelope Grid is turned on and set to eighth notes, and then create new envelopes for Oscil 1 Main Pitch and Oscil 1 Mod Pitch. Temporarily link the Mod Pitch envelope to the Main Pitch envelope. By default, the Main Pitch envelope will be set to Retrigger mode; set the Retrigger counter to 3.500. The pitch envelopes will retrigger every seven eighth notes, which puts them out of sync with the looping amp envelope and creates a shifting pattern of accented pitches. Finally, adjust the nodes of the Main Pitch envelope to produce a pitch sequence you like.

The oscillators will now repeat the pitch sequence an octave apart. To add some counterpoint, copy the Main Pitch envelope to the Mod Pitch envelope (which will unlink it) and adjust its nodes as desired.

Good Filtrations

You can add a lowpass filter with a high cutoff-frequency setting and use its cutoff envelope instead of the amplifier envelope to create the volume pulses. That makes for a more interesting sequence and leaves the amplifier envelope available for additional volume contour. Adding an asynchronous filter-resonance envelope can also add life to the sequence.

To add two more voices to the mix, go to Absynth's Patch window and copy channel 1 to channel 2. Choose different transpositions for the channel 2 Main and Mod oscillators — intervals of a fifth (7 semitones) work well without cluttering up the harmonic landscape. Make the filter envelopes asynchronous by moving the loop-start breakpoint for channel 2's filter significantly (see Fig. 1). You now have channel 3 left for additional counterpoint or a melody.

Len Sasso is an associate editor of EM. He can be contacted through his Web site at www.swiftkick.com.