Commercial Breaks & Beats

Hi, not sure where to post this, so i'll start from here. I'm trying to get my hands on the sound effect that kinda goes.... DUm dum DUMMMMMMMMMM when something surprising happens or when there is a dramatic cliffhanger.

I've heard it twice recently - on that dramatic chipmunk youtube vid and more recently on the IT Crowd as Morris' ringtone.

Anyone help??

Thanks in advance!!!!