Thematic

What's the term for when you type out sounds of stuff?
I want to say onomotapeia, but that's just because I like that word.
It's not the right word.

Anyway, I'm going to type out a word version of a theme song. In the comments, guess the song, then type out your own.

Dun du dun Daaaaaaah
dundu duuuh
Dun du dun DAAAAAAAAAAAAAHHH!
dundu dun dun dun duuuh.