Step into any professional recording studio, and the first thing you’ll notice are the stacks of rack-mounted audio processing gear littering the room. From modular synthesizers to vintage compressors, guitar stomp boxes and arcane drum machines, the process of making music in the modern world often involves having lots of sonic flavorings to choose from, which can quickly become an expensive affair. GarageBand musicians might have condensed their studios down onto a Mac, but that doesn’t mean that there isn’t a vast array of software-based sound modules and effects that work directly inside their audio editor of choice. In the next seven pages, we’ll take you deep into the amazing world of Audio Units expansion plug-ins, which you may not have even realized work in GarageBand. You’ll be amazed at just how deep the rabbit hole goes.

Years ago, Apple created a standardized format for audio plug-ins. It’s called Audio Units (AU), and if a plug-in is delivered in that format, it means that it’ll work inside just about any audio-processing app that works on a Mac—and even some apps like Final Cut Pro. As you’d expect, GarageBand can take advantage of just about any AU plug-ins installed on your Mac, although Apple doesn’t go out of its way to educate GarageBanders about this aspect of the software (see “The Illogic of Logic,”).

While most software installers automatically plop AU plug-ins in the right place, it’s useful to know exactly where they live on your Mac: in a folder called Components, buried inside the Library folder on your main hard drive (Macintosh HD\Library\Audio\Plug-Ins\Components).

If you install  plug-ins by copying them to the Components folder manually, make sure you include any presets. Plug-ins and their supporting files usually come grouped together in a folder. Also, GarageBand should not be running when you copy the files to Components, so quit the app first, then relaunch it. Then, to access AU plug-ins inside GarageBand, double-click on any track in the main GarageBand window (or select the track and press Command-I). Up comes the Track Info window, showing the currently available Apple software instruments. You’re almost there—now click on the Details arrow at the bottom left of the Track Info panel, where you’re given the opportunity to access Audio Units instruments and effects (in GarageBand ’08, there are four effects slots; earlier versions have fewer slots). Click on the checkbox to turn on Generators. When you access the first pop-up menu, notice that built-in GarageBand instruments are listed at the top of the menu, while third-party AU modules appear at the bottom. All of your installed AU instruments and effects should appear here, so select the one you want to use and you can now play it from your MIDI/USB keyboard.

The pop-up menu to the right displays the presets for the selected instrument. If you’ve installed the lovely Crystal freeware synth (and if not, well, do it—see below), for example, clicking on this pop-up reveals a lengthy preset list. This feature doesn’t work for all third-party instruments: Arturia’s wonderful re-creations of classic hardware synths come with loads of cool presets, but they don’t show up in the presets pop-up. Not a problem, however, since you can always access presets from inside an instrument’s control panel too.

Presets are fine and dandy, but the real test of any software synthesizer is in the programming, and by clicking on the pencil tool to the right of the presets pop-up, you’ll be taken directly into the editing interface for the instrument plug-in. Here’s where you can crawl under the hood and mod to your heart’s desire. This editing window remains live while a song is playing, so if you turn on the Loop button in the GarageBand transport controls and adjust the loop duration to the segment of interest, you can play a section of your composition over and over while tweaking the sound to perfection.

You can also apply plug-ins to an entire mix by clicking on the Master Track button at the top of the Track Info pane. You’ll see plug-in slots in the Details area of the pane, and whatever plug-ins you switch on here will affect the entire composition, allowing you to apply a final mastering equalization or compression to everything at once.

Now let’s take a look at some of the tools you should consider adding to your virtual studio. There are two main categories of plug-ins: generators, aka instruments, and processors (which alter the sounds coming out of generators). For simplicity’s sake, we’ve only included plug-ins that are delivered as Universal binaries. 

Software Instruments

These virtual keyboards, drum kits, and other instruments offer an unlimited range of sounds—for less than you’d pay for the real thing. While the built-in GarageBand sounds are definitely fun to play, they offer little in the way of customization or editability, and that’s where third-party instruments enter the picture. The most awesomely powerful software synthesizer, or softsynth, costs a fraction of what the cheapest professional hardware equivalent does, and softsynths often have features that far outpace anything available in the physical world. There’s at least one great softsynth that costs exactly nothing, and the most expensive, deep monsters usually top out at $200. Also keep in mind that most of the software instruments we’re looking at here offer intense levels of programmability, and therefore require some actual effort to master. Our advice: Don’t worry, be happy. And have fun experimenting.