How can I give away music for free download via itunes store?

hello,

I am about to upload a music video, and I would like to release the song as a free download through the itunes store. I would rather not sell it, it's important that it be a free download. is this possible?

I have done some searching online, in various forums, and found posts suggesting it's only possible if Itunes selects your song as a free promotion? is that actually the case? or is it possible to set it up otherwise?

if that is the case, who can I talk to about such a promotion?