Spacing the upper voices

The upper three voices stay close: soprano to alto, and alto to tenor, each within an octave of the next, while the gap between tenor and bass may open wider — the bass is a foundation, not a neighbor. Spacing wider than an octave between adjacent upper voices thins the middle of the texture and exposes the parts; spacing that hugs too closely in a low register muddies it. The classic norm: compact and clear above, room below.

Spacing is the first thing to check when a progression is correct on paper but sounds wrong: gaps in the upper texture read as a missing voice, and thick low thirds read as mud. The octave norm also guides re-voicing — when a line forces the alto out of range, the repair is usually a change of position in the whole chord, not a leap in one voice. Keyboard styles compress toward close position and choral styles open outward, but both respect the same ceiling between neighbors.

• Opening more than an octave between soprano and alto, or alto and tenor, which hollows the middle of the chord.
• Applying the octave limit to the bass as well, and cramping the one voice licensed to stand apart.
• Writing close thirds deep in the bass register, where the interval turns opaque.
• Fixing a spacing problem with one leaping voice instead of re-voicing the chord.

• Ebenezer Prout, Harmony: Its Theory and Practice (1889), The opening chapters on harmony in four parts — The classroom norm: adjacent upper voices within the octave, the bass exempt.
• Carl Philipp Emanuel Bach, Versuch über die wahre Art das Clavier zu spielen, Part II (1762), Part II, on the disposition of the accompaniment — The accompanist’s spacing craft: where the right hand sits and how much room the bass keeps.