Surge XT's Classic oscillator blends pulse, sawtooth, and dual-saw waveforms with sub-oscillator and hard sync

The Classic oscillator generates a main waveform ranging continuously from pulse (-100%) through sawtooth (0%) to dual-saw (+100%) using the Shape parameter. Width 1 controls pulse duty cycle or dual-saw relative phase; Width 2 compresses/expands the waveform in a second dimension. A Sub Mix parameter blends in a pulse sub-oscillator one octave below, sharing pulse-width with the main oscillator. Sync produces hard oscillator sync — the sub-oscillator is the sync master. Unison adds up to 16 detuned copies with modest CPU cost compared to wavetable unison. The unison voices respond independently to scene-level Osc Drift. Classic is efficient and well-suited for subtractive synthesis bass, lead, and pad voices.

Examples

Shape = 0% (saw), Width 1 = 0%, Sub Mix = 30% gives a classic analogue bass. Shape = -80% (narrow pulse), Width 1 = 20% gives a thin reed-like tone.

Assessment

Describe what the Shape parameter controls across its -100% to +100% range. Why does changing the pulse width on the sub-oscillator also affect the main oscillator’s shape?