Harper’s dictionary of music defines our Chromatic scale as "A scale made up of twelve half tones in an octave". A way that we guitar players could look at it would be to play the sixth string on the first fret (this is F) and then play every note on that string all the way up to the 13^th fret. This would give us all twelve notes, or the Chromatic scale.

So when can you use the Chromatic scale? The most common use of the Chromatic scale is when it is used as "passing notes" in a phrase. In other words, when you take a lick that uses the notes from a common scale, and add a couple of notes that are not in the scale. These "passing tones", can be thought of as notes from the Chromatic scale. (Sometimes they sound like "wrong" notes, especially to beginners whose ear hasn’t developed to the point of hearing those outside notes). A common way to add what would be called a Chromatic lick, is to play a scale, and then on one string, just play your fingers in consecutive order – 1, 2, 3, 4, instead of following the scale pattern. There are many more aspects to Chromatic theory, such as Chromatic chords, Chromatic harmony etc. But for now, lets start with a simple lick that starts in key, but then moves us into Chromatic territory.

This lick is from the G Major scale. It starts out by moving up the scale, and then does some string skipping. But all of the first line stays in key. When we get to the second line we see notes added that are not in the key of G. Once again some of these notes may sound "out of key" to you, but as you get it down it will become a smooth transition. Keep at it until you get it smooth.