Waldorf Quantum/Iridium: split stacked layers across the three oscillators

[douglas-carmichael]

Problem

Rompler presets often stack several samples on the same note (e.g. a body layer plus a swell). In the model these arrive as a group whose zones overlap in key (and velocity). The QPAT creator maps one group to one oscillator, so such a preset collapsed onto a single oscillator — only one sample per note survived, and the sound came out thin and quiet.

Fix

Before the groups are reduced to the Iridium's three oscillators, each group whose zones overlap in both key and velocity (i.e. would sound simultaneously) is split into separate layers, and each layer becomes its own group → its own oscillator. Groups without an internal overlap are left untouched, so ordinary multi-samples and velocity-split groups are unchanged. The largest layer is placed first so it drives oscillator 1 and the shared amplitude envelope.

Verification

Converting a commercial E-mu "Orbit" SoundFont (234 instrument presets) to QPAT:

• Oscillator counts now match the source layer depth exactly: 70 single-oscillator, 161 two-oscillator, 3 three-oscillator. For example "Chiffons" (a body + a full-range swell) now uses three oscillators instead of one.
• Presets stacking four layers keep three oscillators (the fourth folds onto oscillator 3 via the existing group reduction).
• Single-layer and velocity-split presets are unchanged.