After 12 notes you come back to the same note, just either 12 notes higher or lower in pitch. Octaves are simply just this. All an octave is, is just those 12 notes, then you have the next octave which is those 12 notes again either higher or lower.

Edit: sorry i explaned that really badly, someone else should explain it better than me. You might be able to find a decription on wikipedia or something.
Last edited by Zakk_Lp at Aug 21, 2009,
An octave of a note is 8 (EDIT: or down) steps up. The octave of G, for instance, is G. G-A-B-C-D-E-F-G. On a guitar, the octave of an open string is the twelfth fret.
For a good example of octaves, listen to Bulls on parade. The very beginning, before the wah riff, is just octaves of F.
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Last edited by Mailbox Guitar at Aug 21, 2009,
An octave is fairly simple. The smaller the portion of string is that vibrates to make a sound is, the higher the note will be. Say that a C note (the string) resonates at 200hz. If you keep going up the neck from the C, so the vibrating bit of the string gets smaller, once you get the string to vibrate at 400hz, that will be a C as well. This continues on so we could assume that resonance at 800hz or 600 hz (right?) would also be a C note.

Edit: It wouldn't be 600. See horseman's post.

tl;dr: (simplified)
A string vibrates at a certain frequency to sound a note. When this frequency is doubled, you get the same note an octave up.
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Last edited by FacetOfChaos at Aug 21, 2009,
^ you messed up about the 600, it doubles every time

take A 440, the octave below is 220hz, the octave above is 880

also for finding the octave on a different string:

on the string below the string you're on the octave will be 7 frets highest from the g string to the b string where it's 8 frets higher

like this


and two strings below it will be 2 frets higher then the fret you're on, except except from the d string to the b string and the g string to the little e

another example:

The octave is the most consonant interval. It consists of a ratio of frequencies 2:1. When these two notes are sounded together, their harmonic series will be almost identical (all overtones of the octave are also overtones of the root). This is not true for any other interval. Because the octave is unique in this manner, it also forms the basis of the repetition of our musical scales. Any note repeated any numbers of octaves higher or lower is given the same name and the same function. This also means that compound intervals will have the same [harmonic] quality as their respective simple intervals (i.e. a 12th and a 5th are considered the same thing harmonically). However, octaves can be utilised when building chords to allow for different voicings, which are different orders of notes, as they are in different octaves, which allows chords with the same function to sound different. Often chords on bass will seperate notes with octaves to avoid sounding muddy.

You can play them as many other people have already said.
Another thing that I didn't see mentioned is that since octaves are the same note, they do not make chords. 3 Cs in different octaves played together will not make a chord.
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