chords · smith1965-introduction-bluegrass

Harmonic accompaniment in bluegrass most commonly involves the use of the three major triads: tonic, subdominant, and dominant, without the seventh. The most common progression of chords is I, IV, I, V, I, which is identical with the basic twelve-bar blues progression (though not always in the number of beats allotted to each chord). The relative minor of the tonic is almost the only minor chord used; it may be stated or only implied by introducing the sixth tone of the scale. In melodies that are apparently close to the gapped-pentatonic scale, the triad built on the lowered seventh degree is added to the tonic and dominant to provide harmonic backing. The progressions I, III, IV; and I, VI, II, V are sometimes used as well. Passage to the dominant chord is, in fact, often accomplished by transition through the super-tonic.