Originally Posted by: Dragon FighterSo those chords are just called intervals, nothing else special?

They are called octaves.

An octave is a specific kind of interval. An interval is the musical distance between any two notes. The distance between the two notes you've been asking about (the lower and higher E's) is an octave. Likewise with the two A's you mention in the later post; they are an interval distance of an octave.

A chord is a group of at least three notes, which is also called a triad. When you only have two notes together, it is called a diad.

So, in very specific terms we've been discussing a diad that is an interval of an octave. :)

This is a technique used by lots of rock players (Vai, Hendrix, etc.), blues players (SRV, Clapton), and jazz players (Wes Montgomery, Jim Hall, etc.). I did a search on GuitarTricks for "octaves". Check it out:
http://www.guitartricks.com/search.php?input=octaves