This is the Maestro Envelope Filter. Thank you! The following is a quote: This auto-wah/envelope filter prioritizes ease of use, allowing for optimal dynamic control with simple operation! It features a 2-mode toggle switch. By utilizing two different filter frequencies, a wide variety of sound-making is possible. The LO mode emphasizes the low frequencies, while the HI mode is set to emphasize the high frequencies. The three control layout allows for quick setting of Sense (filter effect sensitivity adjustment), Attack (filter rise time), and Decay (time the filter is in the open state).