Hearing a string quartet


Let us look at each of the instruments of the string quartet into. The violin is physically the shortest instrument. It has four strings on it going G, D, A, E,  from lowest to highest note. If you look at the strings on the violin carefully, you will see that the G string is the thickest by a long way and the  E string is the thinnest.  Remember what I said about strings vibrating more slowly as they get heavier? The thick string is the heaviest.  This is the G String and it plays the lowest note. The highest note is played by the E string which is thinner than the G String and many times lighter per unit length. Furthermore the E string is at a much higher tension than the G string, which further increasing the frequency of its vibrations, making the pitch of a note that it produces higher. D and A strings between get progressively thinner and  gets higher and the tension also gets higher.

 However, all the strings are the same length. This means that there are only four notes on a violin. This wouldn't be much good for playing music. So how do you get all the other notes? 

If you've read my ramblings about playing in a string trio or string quartet and what it is like playing the instrument, then you already know. You change the length of a string by pressing your finger on it at some point between the two ends. This changes the length of the string that can vibrate. Looking at the equation, the shorter the string the fast it vibrates. So you can increase the pitch of the notes from its open or natural frequency, to higher and higher notes, by pressing on the string further up it.

 So which direction is up on a string? It’s towards the musicians nose. The string is mounted on the instrument by attaching it to a fixing on the violin nearest the musician's chin. It is stretched over what is called a bridge. That is an intermediate support just a short way from its fixing point. The string then has a long length before it goes over another support at the nut of the violin, the point furthest away from the musician. The string then goes around wooden pegs which are turned to increase or decrease the tension on the string.

A stringed instrument has to be tuned. This is the process of increasing or decreasing the tension in the string until it naturally resonates and vibrates at the correct speed or frequency to give the desired notes.  Each note requires a vibration at a different frequency.

For example, the frequency of the notes and their wavelength for a violin, are:

G string: 196.00 Hz 176.02 cm

D string: 293.66 Hz 117.48 cm

A string: 440.00 Hz 78.41 cm

E string: 659.25 Hz 52.33 cm

Once tuned,  the instrument is ready for a skilled musician to play all the other notes that are needed for the music by pressing the strings in exactly the right position to achieve the desired frequency for each note.

The principal is the same for the  viola and for the cello on the string quartet. The viola is very much like a violin but a bit longer, so the strings are longer and produce a lower note. The cello is a very much bigger and the strings are several times longer than those of a violin. They are also very much thicker, being more like fencing wire than violin strings.

So we've been talking about the strings vibrating, but how do they get to vibrate in the first place? This is different on different instruments,  but here we're talking about instruments specifically of the string quartet. There are several ways of making the string vibrate, but the most common is to use a bow. The part of the bow that causes the strings to vibrate are the bow hairs. The bow stick is there to support the bow hairs and keep them tight and to provide complex and subtle springiness to enable various forms of bowing to take place, but this is a specialist subject on its own. Here we are talking about generating and hearing music.

 The bow hairs are traditionally made from horsehair and is still the filament used on good quality bows. Cheaper bows use synthetic fibers.