Newton explained tube amplification via repeated reinforcing motion

Evidence

It plainly appears how it comes to pass that sounds are so mightily increased in speaking trumpets; for all reciprocal motion tends to be increased by the generating cause at each return. And in tubes hindering the dilation of the sounds, the motion decays more slowly, and recurs more forcibly; and therefore is the more increased by the new motion impressed at each return. — Eric J. Heller, Why You Hear What You Hear- An…, 535

Categorization

• DEFINE: Newton’s own words define the proximity/loading resonance principle that the chapter centers on — a historical anchor for the mechanism.
• CANDY: Newton stating the speaking-trumpet amplification principle in Principia is a fun historical fact, though it needs some context about resonance.