Wikipedia says the song was written as an instrumental, then Madonna added words and melody. But it sounds like a single voice and vision.
I’m an admirer of Madonna but not really a big fan of most of her music. The actual songs only rarely rise to greatness, as La Isla Bonita does. But by pure force of will she became, for a number of years, the sexiest, most attention-worthy woman in the world.
I also admire her showmanship and professionalism. Nobody’s ever gone to a Madonna show without coming away impressed. A lot more performers’ concerts would be pushed over the edge from fine to fantastic if they brought her level of dedication and practice and polish to the show.