Rock Band Bass Thingy

So you know the sound that the bass makes before you actually start a song? I've tried to figure out what it is so I can do it at shows just for fun but I've had trouble figuring it out. Does anyone know it? At 0:13 of this video is where it's at.



If anyone has the tab already or could ear it out, I'd appreciate it extremely. Thank you.

Sounds to me like a really quick E(7th fret A string)-A-D. May be wrong though, I just listened to it then tried to find the notes on my bass without checking it or anything.