Tuning — Stretch, Temperament, and Unison

Temperament — just versus equal

Temperament crossfades between two ways of tuning the notes you play:

• Just (left) — intervals built from pure whole-number ratios. A fifth is a perfect 3:2; chords lock together and stop beating. The catch is the one every tuning system runs into: pure intervals only work in one key at a time. Just intonation retunes relative to the lowest note you’re holding — unless you turn on lock tuning (top bar), which pins it to the scale root so the whole key stays consistent.
• Equal (right) — the standard compromise: twelve equal steps, every key equally usable and equally, slightly out. This is what lets you play in all keys without retuning.

Play a sustained fifth and sweep Temperament from equal to just — you’ll hear the beating slow and stop as the interval snaps pure. That’s the sound of just intonation, and it’s hard to unhear.

Stretch — inharmonicity

Stretch detunes the upper partials away from the pure series. At the center (natural) the partials are a pure harmonic series. Push it toward stretch (+) and the highs go progressively sharp — the natural inharmonicity of a real piano string, which is why a stretched setting instantly reads as “acoustic.” Pull toward compress (−) and the upper partials pull in. A little stretch warms up an otherwise clinical additive tone; a lot turns it bell- or metal-like. (The ET marker on the slider shows where equal-tempered spacing sits.)

Unison

Unison detunes slightly sharp and flat copies of each partial and layers them. Off, the sound is clean and single; push toward thick and it widens into a chorused, ensemble character — the classic “more than one of me” richness, applied per-partial rather than per-voice.

Scale and Root

Above the sliders, Chromatic / Root set the scale and key. Leave it Chromatic for no scale clamp, or pick a scale to snap the keyboard and feed the synth’s scale-aware features (the Overtone Scan’s scale mode, the Harmonic Gate). Root sets the key those features center on.

What to Practice

• Hold a fifth and sweep Temperament from equal to just. Listen for the beating disappear.
• Set a clean additive patch, then add a touch of Stretch toward the sharp side. Notice how much more “real” it sounds.
• Turn Unison up under a pad for instant width, then back off until it’s just a shimmer.