Fender MS2 2-Button Footswitch for Mustang Series Amplifiers Connect this 2-button footswitch to your Mustang amplifier (included with the Mustang III, optional for the Mustang IV & V) to enable remote multi-function foot control. Use the Utility menus to assign one of the following functions to the 2-button footswitch: Select presets (up/down), Select Quick Access presets (QA1/QA2), Bypass effects (various combinations), Set TAP interval.