The 1 1/3' mutation, which sounds two octaves and a perfect fifth higher than the note being played, is one octave higher than the 2 2/3' mutation. The 1 1/3' stop may be included as part of the buildup towards the chorus mixture.
Because of its relatively high pitch, the 1 1/3' mutation MAY be added as the highest pitch of a chorus registration to function as a mild substitute for a chorus mixture.