Problem:

Solution:

Garageband distinguishes between AU effect plug-ins, such as Ozone and Vinyl, and AU Generator or Instrument plug-ins, like iDrum. To use an AU effect plug-in as a track insert in GarageBand:

1. Open GarageBand, and create or load a project with at least one track.
2. Select a track, and bring up its Info window. You can do this by clicking on the "i" button in the lower-left corner of the GarageBand UI, or by using the keyboard shortcut Command+i.
3. In the Track Info window, be sure the "Details..." menu (at the bottom) is expanded.
4. The "Details..." menu should allow you to select options for the track's Generator and Effects. Under the list of Effects options, you should see controls for a Compressor and Equalizer listed first, Echo and Reverb listed last, and two pop-menus positioned in between. These pop-menus allow you to apply other GarageBand and Audio Unit effects to the track.
5. Click on one of the pop-menus, and scroll down to the list of effects under the heading "Audio Unit Effects." Your Audio Unit plug-in should appear here. Select its name to enable it as an insert on the track.
6. To view the plug-in's UI and manipulate its controls, click the "pencil" icon to the right of the pop-menu that shows the plug-in's name.