Axis Rod Building

I'm working on a project using copper plumbing parts. This project needs a simple spring-loaded valve to operate a whistle. Obviously, if there is a valve like that in existence that would be ideal, but I haven't found one.

I've been thinking about how to build such a valve myself and the best thing I've come up with is to find a four-way joining piece, like a Tee-joint, and pass a rod through it on one axis with a hole in a strategic position. Does such a thing exist?

Alternatively, is there a simple valve that would do this kind of job? It needs to be air-tight under decent pressure, automatically reset to closed and be opened by a very short movement.

For anyone curious, the project is basically to create something akin to a steam whistle on old locomotives. In this case using compressed air/CO2. I've already built the whistle.