Harmonics:

The term harmonic refers to the bell-like tones you get by damping specific frets on the guitars fingerboard.

It is worth learning harmonics since they can provide you with some very usefull playing effects.

How Do Harmonics Work?

Each time you strike a guitar string, the sound you hear is the result of a number of different components which, when taken together, form what is known as the HARMONIC SERIES.

The dominant sound you hear is known as the FUNDAMENTAL. This is the string vibrating along the full length of the fingerboard between the bridge and the nut, and consequently the element which defines the pitch of the note. However, their are further tones which can also be heard:

These result from shorter frequencies vibrating along different parts of the string, are strict multiples of the fundamental, and are known as HARMONICS, or OVERTONES. The balance between various hamonics and the fundamental is what creates the tonal characteristics of an acoustic note produced by any instrument.

The Harmonic Series:

You can hear a harmonic in isolation by playing a note muted by the left hand at specified points on the guitar fingerboard. The easiest to produce is an OCTAVE HARMONIC.

Place the tip of your finger EXACTLY above the twelfth fret on any string. (Be sure not to ACTUALLY press down on the fret). Now pick that note. All you should hear is a bell-like tone. This is the harmonic, the fundamental having been muted by your finger.

The pitch of the harmonic you hear depends on the mathematical divisions of the string that is resonating. By muting the fundamental at the twelfth fret, you divide the string in half. The twelfth fret being exactly in between the nut and bridge. This is known as the FIRST HARMONIC.

Other types of harmonics are possible too: The SECOND HARMONIC divides the string into three equal sections, the THIRD HARMONIC divides it into quarters, and the FOURTH HARMONIC divides the string into five equal segments.

The frets for these types of harmonics are these: 12th Fret=First Harmonic, 7th/19th Frets=Second Harmonic, 5th Fret=Third Harmonic, In between the 4th and 5th Frets, and the 16th Fret= Fourth Harmonic, and the 3rd Fret=Fifth Harmonic.

Heres a diagram: (They are applicable to any string)
Numbers in brackets= Harmonic Number

E]–12(1st)—7/19(2nd)–5(3rd)–4/16(4th)–3(5th)-
B]————————————————————–
B]—————————————————————
D]————————————————————–
A]————————————————————–
E]————————————————————–

Pinch/Fretted Harmonics

It is actually possible to play harmonics (Pinch, Fretted, or even Fake harmonics if you prefer) for any note on the fingerboard.

What a person does is: they fret a certain note of any string (Lets take 2nd fret of the first string as an example) and the left hand frets the notes in the conventional way, while the right hand simultaniously mutes and plucks said harmonic.

For our example, fret with your left hand the 2nd fret of any string. Now, since every twelfth fret is an octave, rest your index finger lightly on the 14th fret of the string while still holding the 2nd fret.

Now, with your thumb/fourth finger, pluck the note while your index finger is still lightly pressing on the 14th fret. You should hear an OCTAVE HARMONIC.

This can work with any fretted note providing you have sufficient fret range, and you follow the harmonic series with open strings.

I hope this helps with some of your harmonical questions.