In 1964 the Duo-Sonic was redesigned based on the Fender Mustang that had recently been added to the student model line but without the vibrato tail-piece. The student guitars now all featured larger and slightly offset bodies, necks with larger headstocks and rosewood fingerboards and plastic pickguards with the volume and tone controls mounted on a separate metal plate. Pickup selection was moved above the pickups on both the Duo-Sonic and the Mustang and utilized two 3-position on-off-on switches that allowed for in and out-of-phase sounds. The pickups were also reverse-wound/reverse-polarity, which made them into a functional humbucker when both pickups were used simultaneously. Also added in this redesign was the option of a 24-inch scale neck in addition to the 22.5 inch scale. This re-designed model was renamed Duo-Sonic II although decals with and without the II designation were used occasionally. In addition to white, Daphne Blue and Dakota Red colors were added.