Sometimes a lead part can play a figure built around just two notes. In Fig. 6, the lead guitar plays a riff on the root and 7 of F# minor, forming a minor seventh interval: F# and an E above it. The chord progression is Im–IVm–VI–Im–IVm–bII and ends on Im.
The presence of E over an F#5 chord in the minor key strongly suggests F#m7. Over a B5 chord, the E adds the interval of a perfect fourth, making the IVm chord a Bsus4. When the rhythm switches to D5, the riff provides a 3 (F#) and a 9 (E) to form a Dadd9 chord. The second time through the cycle, a G5 chord is played in place of D5. At this point in the lead riff, F# moves up a fret to G. The E is a major sixth above G and the harmony implied is a G6.
Spicing up simple power-chord progressions is an effective way to get some major mileage out of one of the most vital tools contemporary guitarists possess—the root-fifth construction. The effort it takes to get on a friendly basis with intervals and chord qualities will pay huge dividends and is well worth the time spent. Just remember to keep the riffs simple, but not routine. Complexity dwells just under the surface.