final cut pro

To raise or lower the audio at multiple points in a track and create fades and crecendos in your audio, you should create keyframes in your audio clip using the Pen Tool.

First click on the small icon that looks like a mountain on the lower left of the Timeline. This will display the horizontal purple audio level line in the middle of your audio track and allow you to set multiple points or keyframes to adjust the audio level up or down.

Next activate the Pen Tool by clicking on the icon that looks like the tip of a pen on the Tool Pallette (or press the P key on your keyboard). Your cursor will change to a pen-like icon when you move it over the horizontal purple audio level line in the Timeline.

With the Pen Tool, you create keyframes by clicking on the red horizontal audio level line at the points where you want the audio to change.

Then as you move the Pen Tool over a keyframe it will change to a cross. Click, hold down your mouse button and drag the keyframe point higher to increase the audio, or drag it lower to decrease the audio at that point.

Notice that the red line will slope up or down to the other keyframes you've created with your Pen Tool, so the audio will fade in or out between the keyframes.

You also can drag a keyframe to the left or right by clicking on it with the Pen Tool.

To delete a keyframe, click on it and press the Control Key. In the pop-up box that appears, select clear.

For more precise audio editing, you can display the audio waveform - a visual representation of the audio that shows when the audio peaks.

To do this, double click on the audio track in the Timeline, which will open up the audio clip in an audio editing box in the Viewer above.

You can use the Pen Tool in the same way in the Viewer to set keyframes and drag them up or down or to the left or right to adjust the audio levels (you'll see the levels simultaneously change in the audio clip in the Timeline). 

Using the Pen Tool to Fade Video In or Out

You also can use the Pen tool to create similar fades in a video clip. Thus if you have two video clips stacked on top of each other in the Timeline, you can have the top clip fade out to reveal the video clip underneath.

To do this double click on a video clip in the Timeline so it appears in the Viewer.

Then click on the small icon that looks like a mountain on the lower left of the Timeline.

You'll see a black horizontal line appear at the top of the video clip in the Timeline.

Select the Pen tool as described above, click on the black overlay line to create keyframes in the video clip, and then drag a keyframe down to make the clip less opaque - fading out to display any clip underneath.