Page 50 of the Feb. 2021 issue of the EAA's magazine Sport Aviation reports that
Why would the wires hum or sing more when the airstream impinges from one side?
All else being equal, a sideslip converts some of the flow's transverse component to an axial component, from the wire's point of view. (Like many airplanes, the Sea Bird's rigging is mostly parallel to the wing.) That should reduce vibration, because axial motion in a wire under tension is hard to provoke: try bowing a violin with the bow nearly parallel to the string.