Sometimes a specific song will need a single-shot sample to be played at the beginning of the tune (think Sledgehammer, for instance). Here’s how to do that easily with a button in Mainstage: 

1. Open Mainstage. Select a project.

2. Switch to layout mode. 

3. Drag a button into your project window.

4. Switch back to edit mode. 

5. Drag and drop your audio file into the Channel Strips window (I recommend using .aiff or .wav files for this). It will automatically generate a playback track. It should look like this: 

6. Click the button so a blue line appears around it.

7. In the Screen Control Inspector, select Map Parameter. Now select (my audio file name)> Playback>Transport>Play/Stop (switchable)

8. If you want to get fancy, map the button to a midi controller using the “Assign and Map” feature.

9. The Playback plugin will automatically start and stop the track now when you push the on-screen button. If you want it to restart the sample from the beginning each time you play it (my personal preference), open the Playback plugin and select “play from start”.