They are the same as the two LFO's on the Presence UI, except in the Editor they can also be scripted.
LFO stands for Low Frequency Oscillator, and Presence XT has two of them. LFOs create slow-moving regular cycles of control signal that are useful for modulating other parameters over time. One common example is the way many keyboard patches respond when you move the Mod Wheel up from zero; the pitch of the oscillators wavers up and down in an expressive manner, much like the sound of vocal vibrato. This is simply an LFO modulating oscillator pitch to a degree set by the position of the mod wheel.
LFO 1 and 2 have identical controls, so the following explanations apply to both:
- Bypass Click the [LFO 1] or [LFO 2] button to turn the selected LFO on or off.
- LFO Type Choose between Sine, Triangle, Sawtooth, Square, and Random shapes for the oscillation of the LFO.
- Rate Sets the rate at which the LFO oscillates, from inaudibly low (0.01 Hz) for long, sweeping changes, all the way to higher ranges (up to 8 kHz) useful for FM and AM techniques. When the LFO's [Sync] button is engaged, Rate can be set in terms of rhythmic values relative to Song tempo, such 1/8th-note and 1/4-note.
- Sync Engage this option to enable setting LFO Rate to a rhythmic value (such as 1/8th-note or 1/4-note) relative to Song tempo. Disengage to set Rate by Hz.
- Key Engage this option to bind LFO speed to incoming note pitch. Higher notes result in higher LFO speeds, while lower notes result in lower LFO speeds.
- Free Engage this option to let the LFO run continuously, resulting in a differing LFO start point for each note played. Disengage to restart the LFO waveform at the start of each note.
- Delay This control lets you specify an amount of time (in milliseconds) for the LFO to wait before becoming active after a note is played. This lets you do things like adding a bit of expression to held notes, or creating layers of modulation that start at different points in each note by setting distinct Delay values for each LFO.
