Improvisation can be defined as being the spontaneous creation of a melody line. That is, when given a rhythm background (i.e., a chord progression) the improviser is playing a lead melody to blend with it. The improvised lead is spontaneous in that it is not pre-learned (rather, it is done "on the spot"), and it is unlikely to ever be repeated in exactly the same way.
Although improvising involves spontaneity and originality, there are certain scales, techniques and "licks" that all Rock guitarists use. These important fundamentals will be discussed in the following lessons.