The 4–3 suspension

A suspension delays one voice while the harmony moves on beneath it. The delayed tone is prepared as a consonance, held or restruck so that it sounds a fourth above the new bass on the strong beat, and resolved by falling one step to the third of the chord on a weaker beat. The dissonant fourth is the tension; the stepwise fall is the release; the preparation is what makes the tension intelligible.

At any close where the dominant would otherwise arrive all at once: suspending the fourth withholds the chord’s third for a beat and makes its arrival an event. More generally, wherever a voice can hold a common tone across a change of harmony so that it becomes dissonant, the 4–3 turns that held tone into forward motion. Chained one after another over a moving bass, 4–3 suspensions generate whole passages of tension and release from a single device.

• Sounding the tone of resolution — the third above the bass — in another upper voice while the fourth is still suspended, which announces the resolution before the suspended voice can deliver it.
• Striking the suspension unprepared: the suspended tone must appear as a consonance in the previous chord, in the same voice.
• Resolving upward or leaping away — the suspended fourth falls one step, to the third.
• Resolving on a beat as strong as the strike: the dissonance belongs on the strong beat, the resolution on a weaker one.
• Doubling the suspended tone in another voice.

• Johann Joseph Fux, Gradus ad Parnassum (1725), Liber secundus, fourth species (the ligature) — Fourth species is the systematic study of the syncope: a dissonance bound over from a consonant preparation, falling one step to a consonance.
• Johann Philipp Kirnberger, Die Kunst des reinen Satzes in der Musik (1771), Vol. I, the treatment of dissonance — Kirnberger’s essential dissonance: a suspension displaces a chord tone and therefore demands preparation and downward stepwise resolution.
• Ebenezer Prout, Harmony: Its Theory and Practice (1889), The chapter on suspensions — States the three stages — preparation, suspension, resolution — and the rule against sounding the note of resolution against the suspension.