Audio-only crossfades in the whole timeline! Or add multiple sound-only dissolves at the same time to as many clips as you select.
Almost every time I edit, I need to add soft audio transitions between cuts. All of them. Even a smash cut that you WANT to be jarring can create an unwanted "pop" when the playhead jumps from one digital audio file to another.
One of the first things I learned working at CBC in the early 90's is that a 3-frame audio crossfade is the best way to smooth out a sound cut without actually making a noticeable overlap.
One of my main reasons for avoiding Final Cut X for almost two years was the difficulty of adding audio-only dissolves. In FCP 7, you could select your whole timeline, hit command-shift-t, and there you'd have it.
FCPX official workflow is to right-click->expand audio/video, then drag the ends of the audio clips each way so that they are overlapping, then drag the fade handles inwards so that the fades overlap.
GIVE ME A BREAK! For hundreds of edits?! Do I have a sign on my back that says "Please give me carpal tunnel syndrome?"
SO I've been perfecting this workflow and thanks to Alex4D, and a little poking around, I've solved it.
1 - Install the custom motion transition from Alex4d
This puts a new transition in your toolkit: an audio-only crossfade. It will LOOK like it's on both audio and video in the timeline, but it's actually only fading the audio.
You don't need Motion installed to make this work.
You'll need to follow his instructions to install it.
2 -Make that your default transition
Go to your Transitions Browser window.
Find the "Sound Only" transition (you can search for it in the search bar at the bottom)
Right-click the "sound-only" transition in the Transition Browser -> select "make default."
(You didn't know you could right-click on Mac?!)
Don't forget to change this back to something more common after this process!
2 - Set Default transition to 0.1 Second
Go to Final Cut Pro Preferences -> editing -> transitions: duration is 0.10 seconds
That's three frames if you are using 30p, which I do.
But 1/10th of a second should be perfect, just enough to smooth out the cut but not enough to hear any really meaningful overlapping sounds.
3 - Select your whole timeline, or just the clips that need 3-frame dissolves.
Notice I made sure to deselect the titles. Deselect anything that needs no audio transition by command-clicking (cmd-click or ⌘-click) it.
That was quicker than selecting one at a time, for sure!
4 - Command-T to add the transition.
It's that easy! You should see it appear all through your timeline.
You're now done unless...
5 - You need HANDLES on the clips!
If you see THIS:
...some of your clips have no extra media before or after the in and out points. If you add a 3-frame dissolve, each hard cut point will be extended 1.5 frames or so to overlap with the other shot - that's how the fade is made. FCPX will ask if you want to ripple the edits to make the transitions.
This means you have some edits without 1 or 2 frames of "handle" on one side or the other. This is true of any transition.
Depending on what you're doing, you can add the transitions anyway.
Choosing "Create Transition" in that case will nudge everything slightly left (earlier) in order to provide enough audio track to fade out.
If this happens, you will need to check your timeline carefully to make sure nothing has been thrown out of sync.
As Lenny Lipton wrote in Independent Filmmaking (a bible of indie film production): Do Not Develop a Casual Attitude Towards Sync!!!
You can probably catch it if you watch a few bits of the film in which multiple tracks are meant to be in sync. If it's out of sync, UNDO your crossfades immediately unless oyu'd rather fix these sync problems one at a time. It STILL might be easier to do that than to add these crossfades to your whole film one at a time.