A harmonic is an overtone that you hear when you place your finger softly on the string. It creates a whistling sound and in some harmonics, a different and higher note. By not pushing the string down to the fingerboard, the string actually vibrates on both sides of your finger.
There are two types of harmonics, natural harmonics and artificial harmonics. Natural harmonics are created by placing your finger softly on one string without stopping the string with another finger. The string vibrates between the nut and your finger tip and your fingertip and the bridge. There are four natural harmonic notes on each string – one octave, two octaves, one octave and a fifth above the open string, and two octaves and a third above the open string. For artificial harmonics, you place your first finger somewhere on any string and then place your fourth finger lightly above it. This is an artificial harmonic that will sound two octaves above your first finger. In practice, if you see a normal looking printed note that is an open string note that is an open string then you will be playing a natural harmonic. If you see normal looking printed note that is not an open string, then you are playing an artificial harmonic. The small note that that is printed above the love (normal looking note) is where you place your finger lightly on the string.
This is a bullet point explanation of harmonics for strings –
- Touch at the octave, splits string in half, pitch = an octave
- Touch at the 5th, splits string into 3rds, pitch = an octave and a 5th
- Touch at the 4th, splits string in 4ths, pitch = 2 octaves
- Touch at the Major 3rd, splits string into 5ths, pitch = 2 octave and a major 3rd