The Content Editor is used to view and edit the content of a region. All regions in Amped Studio are "hybrid", meaning they can contain both audio and note content in the same region. Double click a region to open it in the Content Editor and select the Audio Editor tab to edit audio.
In the Audio Editor you can change the Gain of the audio clips within a region. The Gain adjustment view is activated by default but can be turned off from the inspector in the left side of the Content Editor. To adjust the Gain of an audio clip within the region, simply click and drag the white gain slider to the desired value.