David Bowie used to do this too!

On his Lodger album from 1978, the opening track was a song called "Fantastic Voyage", sort of a mellow, conversational song about reminding those who shoot missiles to remember the value of human life. But then later in the album comes his minor hit, "Boys Keep Swinging". It had a bombastic production and lots of "up front" back-up singing...but once you dug deeper, it was the exact same chord structure, tempo and key as "Fantastic Voyage".

Also on that same album was "Red Money" which was the exact same instrumental track of "Sister Midnight", a song he wrote for Iggy Pop's The Idiot album...only with totally different lyrics and melody.