Stepper Acid, from Transistor Sounds Labs, is a 16-step sequencer for Eurorack modular synthesizers. It was specifically designed for live performance, though it works well for an array of applications.
Each note entered into the Stepper Acid can have a Gate, Accent, and Slide. There are also dedicated octave buttons that raise or lower the pitch in accordance with octave range, and Forward and Back buttons for toggling between steps. A particularly musical and experimental feature of the Stepper Acid is that steps can still have a pitch, accent, and slide while they are at rest—just like real notes.
Designed specifically for live performance, the Stepper Acid features a Detached function that allows one pattern to remain active while a second is being sequences or chained.