In Surge XT you can modulate one LFO's parameters with any other modulation source

Surge XT allows the parameters of an LFO (Rate, Amplitude, Deform, Phase/Shuffle) to themselves be modulated by other sources. To do this, select the modulation source in routing mode, then click the small orange arrow button on a different LFO to target its parameters instead of selecting that LFO as both source and display. This separates the routing source from the LFO editor target. The practical limitation is that an S-LFO can modulate parameters of a voice LFO, but a voice LFO cannot modulate parameters of an S-LFO (due to voice/scene hierarchy). This enables complex meta-modulation: an envelope can control how fast an LFO sweeps, or a step sequencer can control LFO amplitude for rhythmic depth changes.

Examples

Use an S-LFO to modulate the Rate of LFO 1: as the S-LFO rises and falls, the vibrato speed accelerates and decelerates. Or use an envelope to fade LFO amplitude for a vibrato that intensifies with note duration.

Assessment

Describe the steps to modulate LFO 1’s Rate with LFO 2 in Surge XT. Why can a voice LFO not modulate an S-LFO’s parameters?