Where do Advertisers get their songs from?

Where do Advertisers get their songs from?
We are all here searching for songs, but where do the advertisires find the songs, some are popular but others may not have been used for 20 years and some like techno beats who knows where they found them?

They get their songs from the recording studios. The people making the commercials ask the recording intdustry for sometimes up and coming artists that the record labels want their name to get out there. My friend's mom is the vp of bmi records and that is one of her jobs. Or the directors of the commercials can also just get the songs from their personal collectoin of course

There are also more and more music biz types entering the Advertising World. In a post on this very web site I found a statment to be very true.

Remember that cool kid in your dorm/high school/local bar who used to turn you on to new music? Hard to find, under known music that was expectional?

He/she is now wokring for an Ad Agency.

Another disturbing observation is that there are very few, if any, mainstream media platforms (commerical radio/MTV/mainstream press) that actually promote new and under known music. I mean I get turned on to more new tunes/music via friggin TV commericals than most anywhere else....and I am in the music biz!

I remember in college getting tapes of clips of songs for commercials. I assume either the tapes are sent as promos or you have to pay for them. (I have a degree in radio).