This
is a traditional chanter windcap upgrade, for sets with drones, that allows
the airflow to the chanter to be shut off by gripping the key with the
top hand forefinger. The bottom hand is free to tune the drones, and regulators
if present, with the chanter silenced.
The design is taken from my Dave Williams stop key. A rugged brass key soldered and minimally shaped is mounted into a brass bracket soldered to the windcap. An exterior pad keeps the windcap airtight to feed all its air into the chanter as normal unless the key is depressed. This pulls a rugged brass ball against the end of the air supply tube, shutting off the chanter airtight.
Not recommended for Starter Sets, but worth considering if there's a good chance of upgrading to drones later. $100 for the key, and no extra shipping cost. Sorry, the stop key can't be fitted to existing windcaps.