Turn on the TD20 control unit by switching on the power switch located at the rear of the unit. Press the control unit's "Kit" button, located under the "Drum Kit" heading on the unit's topside.
Select a drum kit key map to edit, using the "Value" knob. Turn the knob until the TD 20 displays the kit you'd like to edit.
Press the "Inst" button under the "Drum Kit" heading and then press the "F5" button under the display. The highlighting around the onscreen "H & R" option disappears.
Hit a drum pad to select it for editing. Use the "Value" knob after selecting a pad to change the instrument for the selected pad. Hit any other pad that you wish to change and use the "Value" knob to assign a new instrument to the pad.
Press the "Kit" button to save your changes.