There's a couple of ways to automate the FADER POSITION (Volume) and the MUTE STATUS during the mix-down. I'm going to tell you about my favorite. Track Envelopes.
Go into the EDIT WINDOW - (Not the MIX WINDOW)
First make sure your tracks are in READ MODE. They are in READ MODE by default. If you look under the R,S,M buttons you'll see a thing that says "AUTO" - next to that it should say READ. If not click on the box and select READ from the drop down. This setting will READ any automation you have applied to that track. You're going to apply some in a second...
If you look at a track in EDIT VIEW you will see underneath the R,S,M buttons a box with "WAVEFORM" written in it. Next to this box is an arrow (really a triangle) pointing to the right.
DO NOT CLICK THE ARROW.
Click on the BOX that says WAVEFORM. Now you'll see some options there, two of which are VOLUME and MUTE. Select VOLUME.
A line appears in the timeline. That line is called an ENVELOPE.
METHOD ONE: Add POINTS (also called NODES) to the envelope using the PENCIL tool. You point to the line where you want to add a node. A little white dot appears. Add a couple to try this out with. Anywhere.
SWITCH to the SMART TOOL (By that I mean click on the BLUE BOX under the trim,waveform, and hand tool buttons) and point to a dot. When you get close enough, the mouse cursor turns into a little hand. Now you can click and drag the point around. Up is louder, Down Quieter. You can also drag it left or right.
METHOD TWO: Forget about the Pencil. Set the Track to VOLUME again as before. Using the SMART TOOL select a portion of your waveform. Drive over to the area INSIDE your selection and ABOVE the line. The cursor turns into some kind of thing that looks like one of those bracket deals turned on its side.
Now you can click and drag up or down and the envelope will change. Once you do that, you can adjust the NODES with the FINGER to fine tune them.
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The Mute Envelope works the same way, except it only has ON or OFF. If the envelope is at the TOP of the track, it is NOT MUTED. If the envelope is at the bottom of the track, it IS MUTED.
Now when you play back your session the volume fader will follow the envelope. You'll see it moving around. The MUTE button will turn on and off as well. Depending on what edits you've done to the envelopes.
Copy and paste this link for an image. You need to copy the whole thing, not just click on it.
http://picasaweb.google.com/natpfunk71/RetardedPhotosIPostOnTheWeb?authkey=9L_acyAOfQc#5243383150190882674