* Diminuendo: This is the musical term for a gradual decrease in volume.
* Decrescendo: A synonym for diminuendo.
* Fade out: Describes a gradual decrease in sound, often used in music and audio.
* Wane: This word describes a gradual decline in strength, power, or intensity.
* Subside: This implies a gradual lessening or calming down.
Example:
* Crescendo: The music swelled to a powerful crescendo.
* Diminuendo: The music faded out in a gentle diminuendo.
Remember, the specific antonym you choose will depend on the context and what you are trying to convey.