Riffs played against minor chords will use notes from the minor scales as discussed in Appendix Two. The main feature of all these scales, is the flattened third note i.e., C natural in an A minor scale as compared to C sharp in an A major scale.
Because the flattened third is also present in a minor pentatonic scale, it is possible to use this scale to construct minor chord riffs. All of the notes of the minor pentatonic scale are part of the pure minor scale.
An example of a riff using pure minor scale notes was given in Lesson 11 (riff 8). This riff uses notes from the A minor natural scale against the Am chord, the G minor natural scale against the G minor chord and the F minor natural scale against the Fm chord.
The following riff features a G# note which indicates that an A harmonic minor scale is being used. Observe the fingering.