Keeley ZOMA Stereo Reverb And Tremolo Guitar PedalThe first sound effects built into amplifiers were tremolo and reverb. Keeleys legendary reverbs are paired with their sultry, vocal like tremolos to give you an unreal sonic experience. Features Simple Control Layout: Three large knobs give you maximum control over Reverb Level and Rate and Depth for Tremolo. Easy Access Alt Controls: Reverb Decay, Reverb Tone, Tremolo Volume. Instant Effect Order Switching: Choose which signal path is right for you.