Volume curve
The horizontal line above an audio waveform in a timeline clip representing the keyframeable volume level in the clip. When you add audio keyframes to a timeline clip, you can adjust the volume at a keyframe, as well as the slope of the curve segments adjacent to a keyframe or between two keyframes, creating volume changes over time.
![A timeline clip showing the audio waveform at the bottom, the volume curve in the middle, and several keyframes added to the volume curve.](https://help.apple.com/assets/6578E613F802FE0EBA0480B8/6578E616F802FE0EBA0480BE/en_US/146b3bf410004f745c8841229e92f0aa.png)