Watch the C Form: Double Stop Exercise online guitar lesson by Dave Celentano from CAGED Commander
A double stop is two notes played at the same time on adjacent strings. Chords are a perfect vehicle for using this device since every two string fragment of a chord can be played as a double stop. The entire exercise fits nicely in the 'C form' pattern except the relocated 17th fret/B string which is borrowed from the 12th fret/high E string, and the 10th fret/A string, which is borrowed from the 15th fret/low E string. Jimi Hendrix was a master at playing chordal double stops and "Wind Cries Mary" and "Little Wing" showcase this in all it's glory.