Lip reeds adjust their behavior in response to reflected sound waves from the instrument.

Evidence

The lips collaborate with the trumpet resonances, by responding to the air pressure in the cup of the mouthpiece. A piston, immune to feedback but producing a waveform with many harmonics, will not faithfully mimic a lip reed, which adjusts its behavior according to the reflected waves. The collaboration is nonlinear—the lips decide what to do only after getting a response from the trumpet air column. — Eric J. Heller, Why You Hear What You Hear- An…, 1540

Categorization

• FICTION: The idea of a nonlinear feedback loop where the player’s own body responds to the instrument’s reply is evocative — a system that decides what to do only after hearing the response.
• XREF: connects to: The player’s lips form a variable double reed making brass a stopped-pipe acoustics — David Howard, Jamie Angus, coustics and Psychoacoustics, 1262; Brass instruments operate acoustically as stopped-end tubes driven by lip reeds — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1234