There are some demos of songs from the first 2 records that have a much different arrangement than the "official" version but the structure is the same. As I said, I think sometimes Madonna actually writes the vocal line. But I doubt she did much more than that. She has always been surrounded by "collaborators", even before she was famous.Like in todays music. I believe it to be the Producers! I can see MJ,but not Madonna contributing! not a gender thing, but a musicianship thing. i mean i can barely tolerate her singing, but watching mj he was involved in every little thing! Madonna is mostly about Image.
100% sure the stuff "co-written" with Patrick Leonard was written by Leonard as for the music, and Madonna only wrote the lyrics.