The notes on string instruments are usually created by changing the vibrating length of the string by ‘stopping’ it with the left hand. An alternative is to touch the string lightly to produce a harmonic. Harmonics are created when a standing wave is set up on the string that divides it into equal parts, the length of which create the new higher note. The simplest is to touch the node half way along a string so that the two halves of the string vibrate creating a note an octave above the open string, but there are many other possibilities.
The natural harmonics that can be produced on the violin are shown in the diagram below.
- the Roman numeral denotes the string (IV = G, III = D, II = A, I = E)
- the small circle shows that it is a harmonic
- the note itself is the sounding pitch (not where you touch the string)
When notating harmonics you should include the string indication as well as the small circle.
This shows cello harmonics (viola is the same but an octave higher):
The use of natural harmonics in this extract create a purer colour to the tone and lightens up the overall sound:
Borodin, Quartet No. 1, fourth movement (Allegro Risoluto)
Natural harmonics can only be created on the notes shown above, but a natural harmonic on any note can be faked by changing the length of the string with one finger (or on the cello and bass the thumb) and then lightly touching the string a fourth above, which generates a very whispery note two octaves higher.
The notation is very precise as shown in the lower staff below, with the sounding note not written. Other types of false harmonics are possible – consult an instrumentation book if you are interested but they are hard to produce and rarely used.
In this famous (and for the cellist terrifying!) example the cello plays muted solo false harmonics as a solo for the first six bars – the effect is cold and magical:
Shostakovich, Piano Trio No. 2, first movement