If a guitar string is tightened, what happens to its pitch?

• A. Higher frequency
• B. Lower frequency
• C. No change
• D. Frequency becomes unpredictable

Answer: (A)

Pitch is determined by the frequency of the string’s vibration. When you tighten a guitar string, you increase its tension. Higher tension makes the string vibrate faster, so the fundamental frequency rises (f is proportional to the square root of tension, f ∝ √(T/μ)). That higher frequency is perceived as a higher pitch. Loosening would lower the tension and thus lower the pitch, while keeping tension the same would keep the pitch the same, and the idea of it becoming unpredictable doesn’t fit the predictable relationship between tension and frequency.