Obviously to use this effectively, you need to know how to play trumpet. It will sound and feel exactly like a trumpet with a straight mute (a mechanical high-pass filter) with a cord attached.
These pickups do pick up extraneous noises like valves and other impacts. The capacitor helps get rid of some of this, but much of this noise is the same frequency range as the trumpet making it difficult to suppress. Its still a fun project to experiment around with and even record a bit of music.
I've attached a sample clip that I made by attaching the pickups to the microphone jack of the computer.
This is my first instructable, so thanks for reading!