G'day Whistleworks,A reciprocal happy birthday from the other side of the globe (mine is a couple of years more ...). I might tootle Happy Birthday to Us on one of my better attempts at a low D whistle.
Actually, the quick PVC mockup I did first works better than the carefully made and proportioned later alloy ones ...! I have not yet made any that cause me not to envy your Copelands.
Regard(les)s,
Bob Bolton