David Cook's got that voice of his cause he is permanently sick.
If I were to sell a product based on his voice, I'd do an advertisement like this:-

"Ever wondered how he got that voice?
Ever wanted to have a voice like his?
Well now you can!! *drum roll*
Re-introducing the oh-so-old virus, the SORE THROAT!! *background cheering*
With a lil' bit of this and that,
You can't get as famous as him (I don't think you'll get anywhere near famous at all. lol),
But well, you can still imitate his voice!!
All thanks to the forgotten virus.... SORE THROAT!!"

Yea, that was random.
What was even more random was how someone (oh, don't act dumb. You know who you are. lol) actually spitted out a teeny bit of Merlion fountain onto me while saying sore throaty guy.
Try spitting while saying that.
I bet your horse money that you can't.
'Cause neither can I!!

-.-''