Source Audio Soundblox Pro User Manual page 17

SYNCHRONIZING THE LFO:
The will start from zero in its pattern every time the pedal is
LFO
switched on or a new tempo has been set using tap tempo. This facili-
tates the synchronization of the to other musicians or recorded
LFO
tracks. Resynchronization will also happen when switching from one
preset to another.
USE WITH AN EXPRESSION PEDAL:
A passive expression pedal can be connected via the Pro's expression
BEF
input. Use an expression pedal to control a variety of functions that can
be set in the Backpage mode (see Backpage Parameters section). For
example, use an expression pedal to manually modulate a filter effect
in the same fashion as a wah-wah pedal, control the speed of an
LFO
effect, switch quickly between effect types, or control the depth and
sweep range of a chosen effect.
Synchronizing the LFO, Use with an Expression Pedal | 17