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Timbral Control

Let's be honest, you probably messed with the controls covered in this section as soon as you figured out that the sustain slider makes sound happen. No matter. Welcome, impulse-informed adventurer — much information & inspiration awaits.

Atrium has a wide range of sonic potential through its three timbral modes — cycle through synthesis techniques by pressing the timbre-mode key (labeled wave fm form).

While each modality has a distinct character, the effects of the sliders are generally consistent in their impact:

  • energy : Adds harmonics when moving away from the centre.
  • timbre : A secondary oscillator which further shapes the output. Typically, this controls the intensity of the effect.
  • tone : Controls the secondary oscillator, revealing more of the identity of the given mode.

Between the energy and timbre sliders is a light bar that displays the harmonic content of the current timbre selection. The fundamental pitch is at the centre, demarcated by the horizontal line. The lights above the fundamental are added overtones (harmonics), while the lights below are undertones (sub-harmonics).

wave

Fresh inspiration drawn from poly-mythologies of the 80's. wave adds a secondary oscillator in parallel to the primary oscillator. This mode offers a cross-fading mix of sub-octaves (either one or two down) and white noise, with simultaneity in-between. Its interface suggests new & dynamic gestures apart from traditional dedicated levels.

energy

Under the hood this is a three-way crossfade between square, sine, and sawtooth waves.

Controls the harmonic energy of the primary oscillator:

  • add odd harmonics: move energy up
  • add all harmonics: move energy down
  • soften to a sine: set energy midway

timbre

Controls the mix level of the secondary oscillator.

As timbre is increased the lowpass/gate will become increasingly overdriven, leading to softly-saturated sounds. Depending on the energy control, this can surprisingly have the effect of softening the sound. Keep this in mind as you explore the sustain modes as it will interact with resonance in the filter!

tone

Fades the secondary oscillator between three different forms:

  • -1 sub octave: set timbre to max
  • white noise: set timbre midway
  • -2 sub octave: set timbre to minimum

The transition between these forms is continuous and provides great opportunity to add just a little noise or sub-octave. This can be great for sprinkling some grit onto a sound.

fm

Two-operator frequency modulation. Capturing many great modular-style sounds, with an interface that makes things much easier to keep in tune. The "modulator" oscillator will accurately track across the full frequency range, so you can dial in precisely the amount of instability you want (or don't want).

Technically Atrium performs phase modulation in order to accurately track pitch. Sonically there is no difference, but this explains the quick pitch-bend when fm is selected if timbre is high. We kept the name "fm" as it's a more widely recognized label.

energy

Controls the harmonic energy of the carrier oscillator:

  • add odd harmonics, move energy up
  • add all harmonics, move energy down
  • soften to a sine, set energy midway

As timbre is increased to the maximum, energy is subtly pulled back toward sine. You probably won't notice, but it pleasantly avoids some strangeness at the extremes.

timbre

Controls the depth of the frequency modulation. At the minimum there is no modulation, while the effect is very dramatic at the maximum.

tone

Fades the ratio of the modulator frequency to the carrier frequency:

  • 2:1 : set timbre to max
  • 1:1 : set timbre midway
  • 1:2 : set timbre to minimum

With the settings between these three positions you'll hear and see sidebands appear. These can be leveraged to create great bass tones below the fundamental.

form

Building on our Mangrove formant oscillator, this is a new shape for a local classic. The primary oscillator is used to create the impulses that you hear. Meanwhile the secondary oscillator defines the frequency of these impulses.

Before exploring form, make sure to set tone to its minimum to avoid immediate confusion!

energy

Controls the harmonic energy of the impulse oscillator:

  • add odd harmonics, move energy up
  • add all harmonics, move energy down
  • soften to a sine wave, set energy midway

energy is highly interactive with both timbre and tone and you might notice that even the midway point can get very gritty! When exploring form it's best to start with energy midway, then use it to add two different kinds of harmonic grit.

timbre

Controls the size of your instrument:

  • for "smallness": move timbre up
  • for subharmonic pitch divisions: move timbre down

Subharmonic pitch divisions are these glorious shifts in pitch that occur at the bottom of the range. They follow the pattern of:

  • down one octave
  • down one octave + a fourth
  • down two octaves

They are the inverse of the harmonic series and are a fantastic tool for adding breadth and dynamism to a patch. This is especially effective when polyphonically modulating timbre to have the different voices sweep through the subharmonics at different moments.

For the curious: these divisions happen when the primary oscillator's impulses are longer than those of the driving secondary oscillator. This causes the primary oscillator to skip some triggers, effectively dividing the pitch. There is a small ambiguous region between each division allowing for multiphonics, where multiple divisions can be heard simultaneously.

tone

An alternative title is "secondary oscillator frequency multiplication" but that's a mouthful! What's important is that tone is incredibly interactive with timbre.

Harmonic relationship:

  • add overtones: set timbre north of centre and move tone
  • add chaotic multiphonics: set timbre south of centre and move tone

When timbre is high, increasing tone has an "oscillator sync" sound, sliding upward through the first 5 harmonics. It can sound like a resonant filter, and works especially well if you drop octave to its lowest setting.

When timbre is in the pitch-division region, tone's effect is quite chaotic, but still reproducible. There is a deep matrix of possibilities here! Due to the combination of pitch division & frequency multiplication, there are many pitches available outside of the harmonic / sub-harmonic series.