String vibration is driven by changing force direction, not changing tension

Evidence

It is important to remember that the bead is always under tension from the filaments. The tension in each filament increases only very slightly (we ignore the effect) as the bead is displaced. It is the change in the direction of the force that drives string vibration; it remains always aligned with the filament. — Eric J. Heller, Why You Hear What You Hear- An…, 772

Categorization

• XREF: Counterintuitive: the restoring force comes from geometry (angle change) not from stretching the string harder; resonates with how tension in real strings stays roughly constant while direction swings. — connects to: A bowed string vibrates as a traveling kink, not as smooth standing waves; Tension directly governs the velocity of transverse string vibrations.; Resonance is universal constructive addition of force-driven velocity — Eric J. Heller, Why You Hear What You Hear- An…, 1012
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 772

Broader Connections

• Tension directly governs the velocity of transverse string vibrations. #complicates (0.75)
• A bowed string vibrates as a traveling kink, not as smooth standing waves #corroborates (0.70)
• Resonance is universal constructive addition of force-driven velocity #expands (0.70) — Eric J. Heller, Why You Hear What You Hear- An…, 1012