He made a decrescendo tinkling, and his lofty features lapsed into their normal mournfulness.
A descending passage, as a return to tranquillity, requires a decrescendo.
When she had to sustain a note for a couple of bars, I was surprised at the beauty of her crescendo and decrescendo.
decrescendo (or diminuendo) al pianissimo means—decrease gradually in power until the pianissimo (or very soft) point is reached.
When she sustains her voice for a couple of bars, I am quite surprised at the beauty of her crescendo and decrescendo.