Using the DualVerb algorithm is one way to 'split the FREEZE'. Two independent reverb drones; separated into higher and lower EQ focus here. The HotSwitch shifts both A-DECAY and B-DECAY from 4 BAR to FREEZE. The expression pedal 'bends pitch' for the lower frequency drone [Reverb B] by changing the SIZE of only one reverb. This 'pitch bend' works with either the default DECAY(s), or on the droning FREEZE, while the higher frequencies [Reverb A] pass through (relatively) unaffected.
Les Paul > H9 > Fender Twin Reverb Reverb B is darker and slightly ahead of A. On the record it sounds like outboard gear panned to the right so this ideally is a Wet/Dry output to 2 amps if you want to get fancy.