ASCAP and BMI don't know what any of it sounds like. They manage the song registrations which amount to showing the songwriter and publishing splits that show what percentage each writer and publisher is entitled to when income is earned. If they have a single registration filed, they will pay out according to that. If you wrote part of a song that was registered with them without including you, in order for them to pay you you'd have to make a claim and the party who made the original registration would have to substantiate their registration. They just pay out, it it's up to the writers and publishers to get the song splits correct.
As far as how they know when to pay out, they sample radio, tv, etc., to get an idea of what's being played. Some radio stations are randomly sampled and for other things like network TV, they are sampling 24/7, meaning if ABC plays your song, you WILL get paid something. This playlist info is provided to them by the stations via logs.
So, in what I think is your case, you'd have to either contact the artist and work out the splits in writing OR wait until you heard the final song and file a counterclaim with the copyright office and the performing rights societies (ASCAP/BMI) and then it becomes a legal matter where you'd still have to work out the song splits except this time it's with attorneys. The later option is the more expensive one so, unless the song is pulling in decent bucks, it's not worth it. Also, ASCAP & BMI will put a hold on the earnings and wait for a resolution from the parties involved.
It's always best to hash out the song splits in writing immediately after writing it. All you need is a simple sheet laying out the song credits and splits, everyone signs with a notary.
When I was involved with music publishing for 15 years, I saw lots of ugly consequences when this wasn't done and the writers were at odds with each other.
Originally Posted by ballerblocking01
Thanks, I get that part but what I don't get is how do the even know what the beat or song even sounds like for them to even track it down in the first place? For example copywrite.gov has a copy of the songs you submit so if you ever ran into legal issues all they would need to do is find the song you submitted to them, copywrite.gov has an actual copy of the track. So what you are saying is BMI and ASCAP just goes by the title of the work you submitted? Meaning if someone just renamed it, made a song to your beat and got the song played at there local stations ASCAP or BMI would not be able to track it because its under a different name than the one you registered the song under?