After choosing a genre and drummer, you can choose from a collection of drummer-specific presets in the Drummer Editor. Presets offer a quick way to browse predefined, region-based Drummer Editor settings, including kit piece pattern variations and fill settings.
In GarageBand on Mac, click the Play button in the ruler at the top of the editor.
The Drummer Editor shows the settings for the currently selected region. You can set the Drummer Editor to auto-select the Drummer region under the playhead, so that the Drummer Editor always displays the settings of the region currently playing.
In GarageBand on Mac, click the Auto-Select button in the upper-left corner of the region in the Drummer Editor.
In GarageBand on Mac, click a preset on the left side of the editor.
The region settings on the right side of the editor update to reflect the chosen preset, and the selected region in the Tracks area is regenerated.