In a recent update, Apple made the iOS version of GarageBand compatible with the popular audio-channeling utility Audiobus. Although Apple provides ways for some apps to communicate with others--Facebook and Twitter hooks built into iOS, for example--until Audiobus came along, moving sound between iOS music apps was a clumsy process that required saving and exporting audio files and then importing them into compatible apps.
What Audiobus brings to the table is the ability for compatible apps to communicate with one another, much as PC and Mac audio applications have been able to do for years. In this case you can designate up to three apps as an audio source--two synthesizer apps and a drum machine, for example--plus another that can apply effects to the sound emanating from the source app, and an output app that is most often used for recording the combined results of the input and effects apps. With this update, GarageBand becomes a compatible output destination.
The Audiobus workflow
To begin, you need at least one compatible input app and a copy of GarageBand for iOS. Audiobus has a webpage that lists compatible apps; or you can launch the Audiobus app, tap the Apps button at the bottom of the screen, and see the same list, complete with links to the iTunes Store.
Launch Audiobus, and you see a simple interface that includes three boxes--Input, Effects, and Output--each bearing a Plus (+) icon. Tap the Input box, and a list of compatible apps on your iOS device appears. Tap one you wish to use, and the box expands--showing a gray box that you tap to launch that app, as well as another box that holds a Plus icon for adding another app. Once the app launches, you should be switched back to Audiobus.
To use the selected app, tap its icon in Audiobus; you'll then switch to that app, and a small palette will appear along the right side of the app's screen. It's from this palette that you can return to Audiobus by tapping a Return icon or move to another app using Audiobus by tapping its icon and then the Return button associated with that app.
As mentioned, you can specify up to two additional input apps. You might do this, for example, if you wish to layer multiple apps as a single input source. Or, if one app is a drum sequencer or an app that includes an arpeggiator, you could have that playing in the background while you jam on a different app. To remove an app, simply tap on the Eject button below or to the side of it.
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