A passage of music where the length of the notes used are halved, for example, where a crotchet was used originally it would be replaced by a quaver. This has the same effect as the music sounding faster although the overall pulse remains the same.
The example below illustrates how diminution works by replacing notes from the original melody with notes of half the value.
Listen to how the opening menacing notes suddenly speed up.
- Augmentation (H)