Most people, who play lead guitar, improvise only in an accompanied surrounding with drums, bass, rhythm guitar and maybe horns. If asked on the spot, to play an acoustic guitar at a party, playing a few leads will bore everybody.
 With the creative ability that they have honed, there is no reason they can't apply the craft to a more chordal orientation. Different styles of music, other than heavy rock, lend themselves to guitar improvisation, such that one, who knows something about chords and scales, may develop a more rounded way to improvise. This way, they don't depend on other musicians to accompany them.
 With that in mind, these exercises demonstrate and open up different possibilities of guitar improvisation.
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Guitar Improvisation In 7 Minutes