La importancia de los vínculos con las sociedades hermanas

Whether starting from a block of stone or ice or a slab of wood, a sculptor envisions an embedded form within that will be exposed over time by chiseling away the material that conceals it (see Figure 4.1). This is an apt analogy to the process the sound designer employs when working in subtractive synthesis. The raw block of material is a timbre rich in overtones like a sawtooth or square wave or noise. In place of a hammer and chisel, the sound designer uses filters and effects. Unlike the finished sculpture, however, time is inherent in sound-based art forms; therefore, dynamically shifting the filters and effects with LFOs and EGs is important for adding variation and interest.

Subtractive synthesis is the first technique covered in this book because it was the first widely used form of synthesis. The RCA Electronic Music Synthesizer, the Theremin, the Moog Modular, and the Buchla 100 all used oscillators as sound generators and filters and other effects as modifiers. This configuration of generator–modifier is central to nearly all forms of synthesis that were to follow. Figure 4.2 Flowchart of subtractive synth. Figure 4.1 William deGarthe’s granite monument dedicated to local fisherman in Peggy’s Cove, Nova Scotia, Canada.

The “subtractive” nature of this technique necessitates beginning with a timbre that is complex and rich in overtones. The source of this sound is a standard waveform (triangle, square, pulse, and noise) generated by an oscillator or played back as a sample from a digital synthesizer. You may have noticed “sine” was omitted from the list of standard waveforms; it is indeed a standard waveform, but one that is of lesser use as a generator in subtractive synthesis because there is only a fundamental, not overtones, to chisel away!

A lot can be done with a single oscillator feeding into a modifier stage, and there are many examples of instruments that do this quite well, but working with two to three oscillators is common and preferable. Figure 4.2 diagrams a simple configuration using Applied Acoustics Systems’ Tassman. Tassman is easy to use, extremely flexible, and a great-sounding synth that is a helpful place to develop an understanding of modular synthesis because it gives you lots of modules to choose from to build an instrument to your liking—plug and play, try things out, you can’t break anything!

Note: See this book’s companion website for details on an evaluation copies and discounts on Applied Acoustics Systems (AAS)

instruments. For what it’s worth, we approached them—not the other way around—because we have a lot of respect for their products.

The flowchart of Figure 4.2 shows a keyboard as the controller. A conventional music keyboard using standard tuning has twelve semitones per octave. Commonly on analog synths, an octave up/down represents a change of ± 1 V, each semitone representing a change of 1/12th of a volt. In this scenario, the keyboard is acting as a modifier to the oscillator by controlling its frequency. The Tassman VCOs show a vertical switch for selecting a waveform: noise, sawtooth, square, and sine. Beneath that is a switch labeled “Range” for selecting the octave range in which the oscillator sits: 2, 4, 8, 16, or 32. The numbers correspond to lengths in feet of a pipe, like those found on a pipe organ on which the smaller lengths resonate at higher frequencies than the larger ones. Playing in octaves can easily be done by choosing a waveform other than noise and setting the ranges of two VCOs to 2 and 4, or 4 and 8, etc.

Notice in Figure 4.2 that each VCO has two modulator inputs: We are using mod1 for keyboard pitch. Turning mod1 to 12 o’clock accepts the incoming voltage signal from the keyboard as standard tuning—the scale can be stretched or compressed by boosting or attenuating above or below that point for unconventional tuning. The second modulation input—mod2—is being used for vibrato. When turned all the way down, the pitch is steady; as it is turned up, the vibrato increases in intensity. The speed and shape of the vibrato come from the wave options in the LFO

module.

The output of each VCO is fed into a separate channel in the mixer for balancing. The mixer’s output then goes through a LPF that has two modulation inputs to modulate the location of the cutoff frequency. In our design, mod1 connects the cutoff frequency with the LFO, cycling regularly over time. Mod2 is coming from an envelope generator so the timbre could, for example, start off brighter with the frequency set high and decay down to a lower sustain level, thus mimicking what acoustic instruments do naturally. The intensity of the cutoff shift is dependent on the level set in mod2. By and large, there is little variation between VCOs used by different manufacturers. Where the real sonic distinction becomes evident is in the design of the filters. A second envelope here is used for volume. Its input is fed from the filter’s output. Turning the sustain level all the way down isolates the attack and decay stages and will emulate a plucked or percussive sound that has no sustain. Turning the sustain level all the way up negates the decay stage because that is the time it takes to go from the maximum level down to the sustain level. Release is the time it takes for the sustain level to drop to zero. For that reason, some instruments will have an AD or AR envelope (rather than the standard ADSR) that assumes a sustain level of zero. Conventional subtractive synthesis with traditional waveforms produces a sound that may seem a little dated. There are times, however, when those are the timbres needed on a given project or as a key layer of a more complex sound. Let’s take a moment to explore some sound designs to get the sound of subtractive synthesis in your mind’s ear, and make the process more familiar. Included throughout the book are “sound designs” to help you better understand the topic under discussion. There is no need to use the exact instrument in our examples; there are many great instruments—both software and hardware—that can be used, and we made an effort to keep the instructions as generic as possible.