With the new support, GarageBand can record audio piped in from standalone apps supported by Audiobus standard. Audiobus is a third-party iOS app that touts "app-to-app" streaming of compatible digital instruments like synthesizers and drum kits to other editing apps.
The compatibility will be an added bonus to many music makers that have invested in the Audiobus platform and want to use GarageBand's flavor of multi-track recording. In recent memory, Apple has not allowed such third-party integration with its mobile offerings.
Along with the Audiobus support, Wednesday's update also brings the option to turn off grid snapping and fixes a feedback issue that occurred when a third-party accessory was plugged into an iOS device's headphone jack.
From the release notes:
Play and record music apps supported by Audiobus directly into GarageBand*
? Turn off grid snapping to get finer control over region and note editing
? Fixes an issue that resulted in feedback while connecting 3rd-party audio accessories into the headphone/microphone jack
* Requires iPhone 4S, iPod touch (5th generation), iPad 2 or later. Audiobus requires a separate purchase.
GarageBand v1.4 comes in at 588MB at is available to download from the App Store for $4.99. Audiobus is a 3.9MB download priced at $9.99.