Supreme Rotary-Speaker Simulator 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. BOSS