Watch the Invention No.4 online guitar lesson by Tony Smotherman from Classical Flatpicking Explorations
Bach makes clever use of the D Aeolian (natural minor) scale with quite a few interesting harmonic modulations. This piece is absolutely perfect for alternate picking and is chock full of cool "guitar licks". Be sure to keep an even and steady tempo throughout. This piece doesn't have to be played at crazy speeds in order to benefit from the useful scale runs, position shifts, and alternate picking throughout.