Loops are wonderful little things. With judicious use of these musical snippets, you can construct entire albums of material from tiny building blocks -- or just scatter a couple over your compositions for flavor. GarageBand comes with a pretty healthy assortment, but spend enough time in the Garage and you may find your songs starting to sound an awful lot like everyone else's.

You're in luck. In a few easy steps, you can create your own loops from nearly any music file you've got lying around.

What you need: Grab a copy of the free, open-source sound editor Audacity. You'll also need GarageBand, of course. And you'll need a suitable file to use as the source of your new loop. This can be most any unprotected sound file: MP3, AIFF, even an iTunes Plus-format song, if you're willing to install the latest beta version of Audacity.

1. Find Your Source
This will probably prove to be the most time-consuming part of the whole process. For the greatest flexibility, look for sound files with stretches of single instruments playing simple, repeated passages of at least a full bar, preferably two (for musical newbies, that's four to eight beats in standard rock time). Longer passages and those with multiple instruments will give your songs a more "live" feel, but will make the loops less flexible. Hint: Look into jazz; often every instrument gets a solo.

Once you've found something appropriate, open it up in Audacity from the File menu.

2. Make Your Selection

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Give the song a couple listens, paying attention to the waveform display to get a feel for how the sections look onscreen. Once you’ve got a good grasp of the section you'll want to use, click-and-drag to select it; you can then drag the boundaries of your selection to fine-tune things.

Give the clip a few more listens with the help of the looping tool: Hold down Shift while clicking Play, and the selected portion will repeat automatically. Pay attention to the timing -- do you hear a stutter at the end? Your selection's probably a bit too long. Does the segment feel somehow "rushed"? The selection might be too short.

3. Clean it Up

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Now we need to pretty it up a bit. With your selection still highlighted, choose Edit > Trim to delete everything in the file except your selection.

If we sent your loop to GarageBand at this point, we'd end up with nasty clicks as the loop repeats. So let's get rid of those: Use the magnifying glass icon to zoom <i>way</i> in, and select a segment around a couple hundredths of a second right at the beginning of your clip. Choose Effect > Fade In to ensure your file starts at zero volume.

Now we're going to repeat the process at the end of the file, this time choosing Effect > Fade Out. Once that's done, give your creation a couple more listens with the looping tool to make sure everything sounds right. If not, try fading larger portions.

Time to move your creation to GarageBand. Choose File > Export as WAV and save the file someplace handy. Open up GarageBand, create a new project, and drag your saved file onto the Tracks column.

4. Nail the Timing

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At this point, you could save your creation in the Loops library, but you'd only be able to use it as a "one-shot," only playable at its original tempo. We want a fully modifiable loop here, so we need to do a little tweaking. First, make sure the Show Measures in LCD and Snap to Grid are checked on the Control menu, and move the playhead (that's the red vertical line) to the numbered measure marker nearest to the end of your loop.

Now choose Control > Show Tempo in LCD, and click on the tempo number in the LCD. Adjust the slider up or down until your loop either ends precisely at the playhead or runs the tiniest bit over. (Opening up the Track Editor and zooming way in with the slider in the lower right makes this much easier.) Once that's done, choose Edit > Split to insert a hard break at the measure mark.

5. Add to Loop Library

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Almost there! Select the portion of your loop before the split and choose Edit > Add to Loop Library. Fill in the fields, making sure Loop is selected as the type (if the option is grayed out, it means your selection didn't end precisely on a measure mark), and "Any" is selected as the Scale -- this will make it easier to find your new loop.

And you're done! Repeat as often as you like; a broad, varied assortment of loops is a powerful tool in any home studio. Experiment with unusual combinations of sounds to create something truly unique. And don't forget: If you've borrowed a sample from someone else's work, make sure you give credit where it's due.