If you can't hear the dialog in a particular movie or your ears are suddenly assaulted with blaring music, you need to be able to adjust your computer's volume as quickly as possible — with a trackpad gesture, for example. With the aid of a third-party utility you can get this set up pretty easily, and we'll show you how.
That third-party utility is the impressive BetterTouchTool, which you can download and use for free. The also excellent MagicPrefs application can be used for the same purpose but it's not quite as straightforward to use for volume adjustments. Get BetterTouchTool up and running on your Mac and you're almost ready to go.
Before you dive in open up System Preferences and disable the trackpad gestures you want to use for changing the volume level (Trackpad, More Gestures). We've used three-finger swipes but you can choose whichever ones you want — just make sure OS X isn't going to try and interfere before you set them up in BetterTouchTool.
With BetterTouchTool up on screen, click Global on the left and then Add New Gesture. Pick your gesture of choice (you'll be warned if it's already in use) and then select Keyboard Keys and Volume Down or Volume Up from the Predefined Action list. Your shortcut is now ready to go — we're just showcasing one handy use of BetterTouchTool but of course you can go to town with other functions if you'd like to.