Close Harmony, Close Harmony

It is different from open voicing in that it uses each part on the closest harmonizing note (such as - C4, E4, G4), while the open voicing uses a broader pitch array (like - C3, G3, E4) expanding the harmonic range past the octave. Close harmony or voicing can refer to both instrumental and vocal arrangements. It can follow the standard voice-leading rules of classical harmony, as in string quartets or Bach's Chorales, or proceed in parallel motion with the melody in 3rds or 6ths.

The folk-rock duo Simon & Garfunkel used close harmony, echoing their chosen role-models, the Everly Brothers.

Source: Wikipedia > Close Harmony