Musical instruments
27 More about strings
What are guitar players doing when they move the left hand around and press a finger down? What do the tuning pegs do? Why do starting violin players sound screechy? Why do string instruments usually have several strings of different thicknesses? This section will apply the standing wave model for strings to answer these and other questions about playing string instruments.
Anatomy of a string instrument
String instruments across many cultures share many elements- a body, a fingerboard, tuning pegs, a tailpiece, a bridge, a nut. At the heart of the instrument is the string. Each string is anchored to a tailpiece at one end of the instrument. From there, the string passes over the bridge, then over the nut and then is wound around a tuning peg. Only the part of the string between the bridge and the nut is meant to vibrate.
Open strings
If the player plucks or bows the string without touching the string with the other hand, the part of the string between the nut and the bridge vibrates. String players call this playing an open string. When you play an open string, a standing waves is formed, with a node at the nut and another at the bridge. The effective string length equals the distance from nut to bridge.
When you play an open string, the string vibrates in many modes at the same time. The result is a complex sound with a distinct fundamental and many overtones. The overtone frequencies are whole number multiples of the fundamental. String players know that you can change the timbre of the instrument just by changing where you pluck (or bow). Pluck or bow close to the bridge and the sound is harsh- full of higher overtones. Play further from the bridge and the sound becomes more mellow- you get more of the fundamental and lower overtones and less of the higher overtones.
Tuning pegs
The tuning pegs are designed to adjust the pitch of the open string. The pegs work by controlling the tension of the string. Tightening the string increases the speed of waves in the string.
Stop to think 1
What effect does tightening a tuning peg while playing an open string have on wavelengths of standing waves on the string? How does it affect the pitch? Explain your answers, based on the model of the string.
Different strings
Most string instruments have several strings, each with a different composition and/or thickness. On many string instruments like violin and guitar, the strings all have the same length because they share a single bridge and a single nut. Using strings with different density with the same length allows for very different pitches at roughly the same string tension. (Keeping the tension roughly equal across all strings has benefits for the player as well as the instrument).
Stop to think 2
Explain why the heavier strings on a guitar produce lower notes, even if all the strings are strung at the same tension. Use the equation [latex]v=f \lambda[/latex] in your answer.
Fingered notes
To change the note th