Apple Logic Pro X - Manual (Page 402)

Chapter 14 Edit the timing and pitch of audio 402
Change the gain of audio regions in the Audio Track Editor
When Flex Pitch is turned on in the Audio Track Editor, you can adjust the gain of individual
audio regions from –30 to +30 decibels.
Adjust the gain of an audio region
1 To turn on Flex Pitch, click the Flex button in the Audio Track Editor menu bar.
2 Choose Flex Pitch from the Flex pop-up menu in the Audio Track Editor menu bar.
3 Select the regions you want to adjust in the Audio Track Editor.
4 Drag the Gain slider in the Audio Track Editor inspector horizontally to adjust the gain.
Gain slider
For more information about Flex editing, see Flex Time and Pitch overview