Attaching mass to a string lowers odd harmonics and can trigger chaotic screech

Evidence

If the deviations from harmonicity become severe, and involve more partials, cooperative resonance and phase locking may lose their grasp, resulting in a chaotic breakup and an unpleasant screech. This is exactly what happens when a small piece of tape or putty is tightly attached to the string at various places. If the object is attached in the center of the string, all the even partials, which have a node there, are barely affected, and all the odd partials, which set that part of the string in motion, are lowered in frequency due to the extra mass. With a very small amount of tape or putty, the string remains bowable but has a different timbre. If the string is plucked and the sound recorded, the somewhat strange resulting tone can be Fourier analyzed, with the result that all the odd partials are lowered in frequency compared to their perfectly harmonic counterparts. With slightly more tape added (still a surprisingly small amount), the string becomes unbowable, except for a screeching sound. — Eric J. Heller, Why You Hear What You Hear- An…, 1812

Categorization

• QUESTION: Why exactly does extra mass push the string from bowable cooperative resonance into chaotic breakup? The phase-locking breakdown mechanism deserves deeper study.
• ADDENDUM: The cooperative-resonance-loss mechanism here parallels how grafted or structural modifications destabilize systems, echoing the trees-as-infrastructure theme of structural resilience.
• DEFINE: Great practical illustration of how partials, nodes, and harmonicity behave under perturbation — even/odd mode splitting is a clean teaching case.