If you use GarageBand — like I do — you probably have encountered a few things that appear to be undocumented features and wondered what they are for. One such puzzle for me was the color-changing “playhead” arrow at the top of the timeline. Most of the time it is white, but it turns yellow, orange and red as well.
At times, I’ve thought it would reveal zero-crossings, clipping, sections of silence, or a few other things. It turns out to mean none of those things.
I’d call it a mood ring: it gets redder as your computer works harder to play back your audio. So, if you see it changing color, close some other programs, or lock some tracks in GarageBand to cut down on CPU usage.