Processor overload: curing red(play)head syndrome

So you've just put the finishing touches to your latest magnum opus, adjusted the Phaser and Amp Simulation effects on each of your 32 Software Instrument tracks to perfection, added a shade of Vocal Transformer to each of your 64 Real Instrument tracks, and now it's time, finally, to hear your creation in all its magnificence. You sit back, click play, and get:

Congratulations! You've just overloaded your processor.

The signs were there

How can you tell your processor is about to be overloaded when you can't see the silicon sweat dripping from its overworked brow? Fortunately, GarageBand provides a temperature gage in the shape of the colour of the triangular playhead that moves along the top of your GarageBand song when it's played.

Keep an eye on it as you play through a song and you'll see it change:

	White playhead. GarageBand is breezing. A cocktail pianist in the slow hours.
	Yellow playhead. Working, but not sweating. The Moonlight Sonata.
	Orange playhead. Earning its keep. Barrel house boogie-woogie.
	Red playhead. Close to overload. Jerry Lee Lewis pounding out Great Balls of Fire.

It's the red playhead you want to avoid. Once you see that for any length of time, you're at risk of playback breaking up or stopping. (You can add more tracks even once red shows, but GarageBand's interface soon becomes sluggish and almost unresponsive.)

So what can you do?

You don't want to sacrifice your magnum opus just yet. (Remember all those hours spent tweaking the Phaser settings?) Fortunately, there is a solution less costly than buying a new triple-processor G5, in the shape of the little padlock icon attached to each track from GarageBand 2 onwards. Click it, to make the padlock glow green, and you've locked a track.

What does this mean? In practice, it means you've taken a processing load off GarageBand's shoulders and it can play your effects-laden tracks as easily as it would a simple AIFF sound file.

And how can it do this? Simply because that's exactly what it is doing — playing a simple AIFF sound file instead of your complex effects-laden track. After you've locked a track or two and press play, you'll see a progress bar as GarageBand locks the tracks:

What GarageBand is doing here is rendering (i.e. recording) the locked tracks, individually, along with all their effects and settings, to disk. From this point on, till you unlock the track (or modify it in any way), when GarageBand plays back your song, it will be playing the sound file rather than generating the instruments and effects on-the-fly. (It only goes through this locking process on the first playback after you lock a track.)

Finding the locked tracks

Where are locked track audio files saved? In the GarageBand song file. GarageBand saves its songs as packages, which are sort of like folders in Mac OS X, only it's not immediately obvious they are folders.

To find the sound file of the locked track, locate the GarageBand song file. Right-click it (or control-click if you've got a one-button mouse) and choose the Show Package Contents option. This will open a new Finder window with the actual contents of the GarageBand song.

Locked tracks are stored in the Freeze Files folder. (If you haven't locked any tracks, you won't see it). Open this folder and you'll see something like this:

The file you see is a recording of the track you've locked. You can open it in QuickTime or any audio file app and play it back. (Note that the recorded file is the length of your whole song, even if the track you locked doesn't play for the whole song. In which case, there might be a few silences when you play it back.)

Lock and load

This might seem like only mildly interesting information, but there is more to it. Now you have your track, nicely rendered with all its effects and panning and so on, you can drag the file into a different GarageBand song (which copies it into that song's file) — for instance, if you're building up a very carefully-crafted or complex song out of several others (you know who I'm talking about, you prog rockers out there.)

Why is this useful to know? Well, the official line according to GarageBand Help is that, to do this, you should solo the track you want to copy, then export it to iTunes, then find the iTunes file and drag it into the song you want to duplicate it in, and then, unless you want a really messy iTunes library, remove it from iTunes.

As you can see, the "lock and drag" approach is a bit quicker, and saves you having to open iTunes.

For more tips on optimising GarageBand playback, see Optimizing GarageBand performance in the GarageBand help file.