From the Beatles to Jeff Beck, Santana to Stevie Ray, many guitar greats have incorporated the rotary speaker into their rigs. With this in mind BOSS proudly presents the RT-20 Rotary Sound Processor. Employing COSM-modeling technology, the RT-20 authentically reproduces classic rotary-speaker sounds. It offers adjustable Rise Time, Horn and Bass speed, Overdrive, and more. And not just for classic twirl, the RT-20 can be used to create unique overdrive and pulsating effects as well. This pedal sounds amazing, and offers a stunning graphical view of the virtual rotors on its built-in display..