Based on the article by Michael Droste at TrumpetStudio.com.

Is precision valve alignment one of the most valuable services you can get for your trumpet, or the most sophisticated snake oil ever sold to brass players? In Episode 24, Adam and Bella dig into a question the trumpet world has argued about for fifty years and still hasn't settled.

They start with the mechanics. A piston valve has ports that must line up with matching ports in the casing, and what determines that alignment isn't the brass machining at all. It's the humble stack of felt, cork, rubber, or neoprene bumpers under the finger button. Yamaha's own technical data shows felt thickness can vary by up to twenty thousandths of an inch within a single batch, and it keeps compressing with oil and use. Put that against the three thousandths of an inch that separates a med ...