Alteration

What it means

Alteration is the chromatic change of a chord note: a note is raised or lowered by a semitone without the chord losing its function. The sonority remains what it was, but gains a sharper direction, because the changed note now lies a semitone from its goal and presses toward it.

In the notation

Alterations are recognisable by accidentals that do not stem from the key signature. The spelling follows the direction of the resolution: a note that goes on upward is raised, one that goes downward is lowered. Notes that are the same in sound can therefore be notated differently, according to where they lead.

Musical use

The sense of alteration is the creation of additional leading tones. Where the diatonic scale has a whole tone, a change produces a semitone and with it a tension that calls for resolution. In function theory the alteration is indicated by additions to the function symbol; the sonority keeps its functional name.

Some altered sonorities have established themselves as fixed formations: the Neapolitan sixth chord with the lowered second degree, the augmented sixth chord with outer notes straining apart, the dominant with raised or lowered fifth. In the nineteenth century alteration was driven ever further, until the boundary between altered tonality and free chromaticism blurred.

Alteration is to be distinguished from the secondary dominant: this too contains notes foreign to the scale, but as a leading tone to another degree, not as a change of an existing chord note. And from modulation it differs in that the key is preserved.

Altered notes are clearly to be distinguished from mere accidentals: a sharp in a sharp key or the raising of the leading tone in minor belongs to the key itself and is no alteration in the harmonic sense. A note is altered only when it chromatically recolours the diatonic chord and thereby gains an additional tendency. In Romanticism alteration increases, until the chords in Wagner and later often become ambiguous.

Performance practice

In altered sonorities find the changed note and follow its direction; there the effect lies. Lead it on in a directed way and intonate raised notes rather high, lowered ones rather low. And take the sonority as a tension, not as colour alone — it wants to be resolved.