Vocal folds drive the tract one-way, unlike the interactive trumpet feedback loop

Evidence

The vocal frequency and waveform are largely determined by the muscles of the larynx controlling the spacing and especially the tension in the folds. In other words, the vocal fold system is a high-impedance drive that does not vibrate appreciably differently because of its coupling to the vocal tract. In contrast, the lips of a trumpet player are subject to nonlinear feedback from the resonances of the trumpet tube, leading to interactive cooperation. — Eric J. Heller, Why You Hear What You Hear- An…, 1663

Categorization

• XREF: High-impedance drive vs. nonlinear feedback is a classic control-theory distinction, connects to musical acoustics and the earlier analogy chapters.