after you saying it was orchestral - for some reason I adopted a 3/4 waltz. I also didn't recognise the melody, but the chord progression - if you slip in an F instead of the Dm (though arguably interchangeable due to relative relationship) I recognised GnR's Ain't It Fun! Somehow doubt it was the orchestral piece you heard though

https://www.youtube.com/watch?v=wApjy0IaCTw