If you want to get a complete unsderstanding of how it works from someone who's done it a few times now (an insider) the can I suggest to you all that you get a copy of a book called "The Manual - How to have a number one the easy way".
For sure, he talks about how you 'sell your soul' to the record companies, IE Produce a track that sells. It's a pretty tongue in cheek tale and by no means a big book with quite a humourous writing style. Shit, it even has a money back guarantee.
Written in 88 he talks about hiring studio time and how in the next decade the Japanese will 'probably allow us to do this stuff in our bedrooms.' (What a prophet! 'cept it wasn't the entirely Japanese)
Can't remember his name of the top of my head but he did it in the 80's with tunes like "Doctorin' the Tardis" as the Timelords, in the 90's as the KLF with as string of number ones, and recently you may have heard an awful tune by someone called Scooter. I think the songs called "The Logical Song" or something like that. Pure crap but every one of these tunes is written to formula and fuck me if it doesn't work.
I have written a couple of tunes to this formula and I'll tell you this. 1.) It makes writing a track 10x easier, like painting by numbers. Each tune has had better response from my audience and record company producers than any thing else I've done by a mile. You CAN still throw your own brand of style at it.
If nothing else its a great read and any muzo will love it whilst possibly hating it at the same time and gets some laughs along the way. Its difficult to find but worth getting hold of.