Parts of a heart or trumpet

VALVES

Think of the mechanical flaps that control flow—one keeps blood moving in the right direction, while the other helps a musician hit the right note.

This clue plays on the double meaning of "valves," which are found in both the human heart and a trumpet. In the heart, valves regulate blood flow between chambers, while in a trumpet, they’re the buttons pressed to change pitch. The word itself fits neatly in both contexts, making it a straightforward but clever answer.