This is I think one of the most known Age of Empires II songs from the soundtrack. It summarises the atmosphere going on on the game and is usually heard at the beginning of the game (that's my experience usually)
It has pretty interesting instrumentation from flute to synth string in the original. My intention was to make original sounding sounds, and in most part it worked. However, some alone sounds are taken from the original to get the feeling, still keeping the updated soundscape.