Cheers!

Guitarists can force these harmonics to sound by touching a finger on the vibrating string.
If you touch at the 12th fret you force the string to vibrate in two halves, producing the 2nd harmonic, an octave above the fundamental. If you touch the string at the 4th fret you force the 5th harmonic, which is the 3rd of the chord. (On the bottom E string you would get a G#)
If your guitar string is is 25 inches long, the 5th harmonic (the 3rd of the chord) is encouraged by playing or strumming about 7 or 8 inches from the bridge. On my acoustics, this is just above the sound hole. Plucking the E string hard here, and listening, one can hear the 3rd of the chord (the G#) sounding quite clearly.
The same applies to electrics.
Hope this helps.
* There is a lot of confusion and disagreement over the meaning of the words overtone and harmonic. I have used the convention where the lowest note (fundamental) is also called the 1st harmonic. The 2nd harmonic, the octave above, is referred to as the 1st overtone, and so on.

The reason it sounds as "powerful" (partial pun intended) as it does is because of the overtone series which creates the third in a way which is more detailed than i care to explain, but suffice it to say that the third is there, but not in the traditional sense that would be associated with in chords.

Please do go into detail!  The physics of sound is well beyond me, but I know waveforms do strange things when blended and mixed.  I'd be really interested in hearing about it.

A power chord is conceived of and intended to be a triad with the "third" note omitted (thus it is neither major nor minor).

Precisely.  That leaves you with an interval of a perfect 5th.

The tonality of triads is determined by the 3rd.  If you omit that, you're left with two notes, i.e. an interval.

Just curious, when did the term "power chord" come into being? my early recollections of the word "power" was associated with the early "hard" rock sounds of groups like deep purple,zeppelin,Hendrix ect.. what gives this form the "power" over any D or A shaped bar position?

Power chords were introduced by Link Wray in his hit 1958 instrumental "Rumble".Wray utilized the power chord during an improvised show in Fredericksburg, Virginia. Before "Rumble", electric guitars were commonly used to produce clean sounds and jazz chords. Wray pioneered electric guitar distortions, like overdrive and fuzz, and was the first guitarist to use power chords to play a song's melody.

The first hit song built around power chords was "You Really Got Me" by the Kinks, released in 1964 .

Early heavy metal bands such as Black Sabbath and Deep Purple also helped to popularize power chords.

Pete Townshend, having been influenced by Link Wray, is often credited for introducing the term and the power chord in general and is an avid user of them.

If you look into 4 string, or D shaped barre chords, the B string is used as a perfect 5th interval.
Example; E chord XX2454
                 F chord XX3565
                 G chordXX5787
                  A chordXX7 9 10 9
                     etc.............

Those aren't power chords.    That's just a closed D shape, giving you a proper major chord.   A power chord is *just* the interval.

jerome.oneil wrote:

A "Power chord" is really just an interval of a perfect 5th.  You can take that shape anywhere down the neck, or across it to the B string, and you're playing a "power chord."

Uhm nope ...........

ummm... sortal

Right.  I'll get that right some day.

If you're playing the b string, it's no longer an interval of a perfect 5th.    "Power chords" aren't chords at all.  They're just intervals, so *any* shape that provides that interval will work for you.

A "Power chord" is really just an interval of a perfect 5th.  You can take that shape anywhere down the neck, or across it to the B string, and you're playing a "power chord."

Uhm nope ...........

2 problems here.

1) it's up the neck, not down the neck ( going from fret 3 to fret 9 is an upward ascent, going from fret 9 to fret 3 is a descent)

2) playing the b string on an A shaped barre chord will work sometimes but not if a minor chord is involved in the progression. Now maybe you're confusing the A shaped barre chord progression with the suspended second position, (ie X02200, x13311,X24422, etc..). In this example (using the sus2nd's the b string theory will work, but only with this ,( granted no minor chords are in the progression)................