9. The Overtone Series and Timbre

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When you pluck the A string on a guitar, it vibrates back and forth 110 times per second (or at 110 Hz). The vibration is then passed on to the hollow body of the guitar which vibrates at the same rate as the string, and amplifies the sound. But when you pluck the string, it doesn’t just vibrate back and forth at that one frequency. Actually, it vibrates at many different frequencies all at the same time, the lowest of which is 110 Hz – this is called the fundamental frequency.

But because the string is fixed at both ends, it can only vibrate in multiples of the fundamental frequency:
- The whole length of the string vibrates at the fundamental frequency of 110 Hz (this is AKA the 1st harmonic)
- The string can vibrate in halves = second harmonic (or the first overtone) at 220 Hz
- The string can also vibrate in thirds = third harmonic (or the second overtone) at 330 Hz
- The string can vibrate in quarters = fourth harmonic (or the third overtone) at 440 Hz
- And so on…

This is called the Overtone Series or the Harmonic Series – and it’s the basis of how we structure music, as we discover over the next few videos.

Some of the animations in this video were sourced from the below websites. A big thank you to them.

Title: Vibration_corde_trois_modes_petit.gif
Author: Christophe Dang Ngoc Chan
Link: https://commons.wikimedia.org/wiki/Fi...
License: Creative Commons Attribution-Share Alike 3.0 Unported

Title: Vibration_corde_trois_harmoniques_combinees_petit.gif
Author: Christophe Dang Ngoc Chan
Link: https://commons.wikimedia.org/wiki/Fi...
License: Creative Commons Attribution-Share Alike 3.0 Unported

Title: Bowed violin string in slow motion.gif
Author: ViolinB0W
Link: https://commons.wikimedia.org/wiki/Fi...
License: Creative Commons Attribution 3.0 Unported