Diminuendo
Getting quieter, synonymous with decrescendo.
What it means
Diminuendo denotes a gradual decrease in volume and is synonymous with decrescendo. Both terms come from Italian and are used interchangeably in practice; which one a composer prefers is often simply a matter of habit or national notational tradition, without any difference in sound attached to the choice.
In the notation
Diminuendo is usually notated with the abbreviation dim. above the staff, often followed by a dashed continuation line for as long as the fading lasts. Equally common is the hairpin, a wedge shape narrowing to the right, which indicates the same gradual decrease in volume as the word abbreviation.
Musical use
A diminuendo shapes the tension of a phrase or section and is often combined with a slowing of tempo or a harmonic resolution, for instance at the end of a movement or before a general pause. A diminuendo should be distinguished from a subito piano, a sudden, unprepared change in volume without a gradual transition, and from terms such as morendo or diluendo, which suggest a dissolving of tone quality in addition to volume.
Performance practice
Plan a diminuendo across its whole length rather than getting abruptly quieter only at the end; spread the decrease evenly or, depending on the musical context, accelerate it toward the end. Take care to maintain sound quality even at low volume, so the tone does not become unstable or thin.