Harmony. Harmonic focus on G-D filled in as G-B♭-D, which emerged in the previous block to challenge the primacy of D-A, now takes over decisively. It is five semitones from the principal melody (spanning C-G) and two semitones from the inverted contrapuntal accompaniment (spanning A-E). As in previous blocks, the intervals of displacement between melody and harmony are major seconds and perfect fourths/fifths, creating a persistently diatonic environment. As the music moves from block to block, the harmony and melody shift in relation to each other.