Partials 1 and 2 are a pair and partials 3 and 4 are a pair. The partial structures work identically for the two pairs. To simplify things, I will only use the first pair.
The Fantom visualizes the structures (in ZOOM mode) on the display. The visualization is useful, however, not trivial to understand. Partial 1 is often called the carrier and partial 2 the modulator.
The structures allow us to change the harmonic content of the oscillators, and more specifically, they allow us to change the harmonic content over time with envelopes, LFOs or manual controllers. When experimenting with partial structures, I recommend to also use an envelope that modulates some parameters related to the partial structures.
SYNC: It mimics the sync functionality of analog synthesizers. It only works when both partials use the oscillator types VA or PCM-Sync. The partial 1 oscillator is reset at intervals of partial 2’s pitch cycle, and the effect depends on the pitch difference between the two oscillators. Typically, the pitch of partial 1 is modulated with the pitch envelope or an LFO.
RING: In Zen-Core, ring modulation combines the direct output of oscillator 1 with the final output of partial 2 (after the filter, EQ and amp, in contrast to many other synthesizers where the direct outputs of two oscillators are combined). Ring modulation works with all oscillator types. It produces nice results if the pitch ratio of oscillator 1 to 2 is simple (e.g. 1:3). It has 3 output levels: osciallator 1, partial 2 and the combined signal. Envelopes and LFOs are often used to modulate these levels.
Example: Set the pitch of osciallator 2 to +19 semitones (i.e. 3x base frequency). The combined signal will contain a mix of 2x and 4x the base frequency.
Notes:
- Ring modulation is symmetrical in the sense that modulating A with B is the same as modulating B with A. In Zen-Core, there is some additional flexibility because the second signal is going through the filter and amplifier before being combined with the first signal.
- The ring modulation levels can only be modulated via the control matrix of partial 1.
- The structure can be used to pass a signal through 2 filters, 2 amplifiers, with 6 envelopes and 4 LFOs. The levels for oscillator 1 and the combined signal can be set to zero.
- Ring modulation can cause aliasing effects.
Notes:
- Cross-mod depth can be set to zero to disable frequency modulation. The structure can be used to merge 2 oscillators before the filter stage, similar to the signal path on analog synthesizers.
- The cross-mod levels can only be modulated via the control matrix of partial 1. The pitch envelope and the LFOs of partial 2 can be used to modulate ATT of oscillator 2, which sometimes frees up an envelope/LFO of partial 1.
Example: Use the same pitch for oscillator 1 and 2, set cross-mod oscillator 1 level to 127 and cross-mod oscillator 2 level to 0. Use a partial 1 envelope to modulate cross-mod depth or the partial 2 pitch envelope to modulate oscillator 2 ATT.
Notes:
- The cross-mod levels can only be modulated via the control matrix of partial 1. The pitch envelope and the LFOs of partial 2 can be used to modulate ATT of oscillator 2, which sometimes frees up an envelope/LFO of partial 1.