Surge XT provides four inter-oscillator FM routing topologies controlling which oscillators modulate each other

Surge XT’s oscillator FM section provides four routing topologies distinct from the standalone FM2/FM3 oscillators. No FM disables inter-oscillator FM. 2 > 1 uses Oscillator 2 as a modulator of Oscillator 1. 3 > 2 > 1 chains Oscillator 3 modulating Oscillator 2, which modulates Oscillator 1 (a linear FM chain). 2 > 1 < 3 has both Oscillators 2 and 3 modulating Oscillator 1 simultaneously (parallel modulation). The FM depth slider controls the modulation amount. This routing works with any oscillator types — you could FM modulate a Classic oscillator with a Wavetable oscillator, or a String with a Sine, for unusual timbres. This is additive FM on top of the normal oscillator output mixing, different from Chowning-style pure FM where only the carrier output is heard.

Examples

Set Oscillator 1 to Sine, Oscillator 2 to Sine, routing 2 > 1, FM depth moderate — creates classic two-operator FM sidebands on Oscillator 1 while Oscillator 2 still plays through the mixer.

Assessment

How does the 3 > 2 > 1 FM routing differ sonically from 2 > 1 < 3? In Surge XT’s inter-oscillator FM, does modulator output appear in the final signal? Explain how this differs from standalone FM2/FM3 oscillators.