The moment that 'Die' and 'Hard' slam together onscreen to an ominous low-chord on strings mixed in with jingling sleigh bells it announces the arrival of John McClane, his dark Xmas, the ground-breaking franchise, and Michael Kamen's score with immediate seriousness. It's as if the music just went "gulp!"
When I was 8-years-old I was off school sick (one of several million of such instances) and Die Hard was rented on VHS to pacify me while I lay on the couch under a quilt. It changed my life. Yes, the film did leave THAT much of an impression, and not the least of its attributes was Michael Kamen's unusual score, which is still very unique and hard to describe 24 years on.
Despite strong recurring themes and numerous scene-specific individual ostinatos and melodies, the strongest impression of this score is the atmosphere, which frequently conveys the lonely, unfinished Nakatomi Plaza and the cold air echoing around in the hollow air ducts and passageways. Kamen constantly quotes 'Winter Wonderland' and Beethoven's 'Ode to Joy' throughout (a technique he repeats in Die Hard 2 with 'Finlandia' and Die Hard 3 with 'When Johnny Came Marching Home'), creating a chilly, Xmas feel despite there not being a single snowflake seen in the California-based movie.
Like John Williams' Home Alone scores, much of Die Hard feels out of place if you play it outside of the season, but tracks like 'The Battle/Freeing the Hostages' and 'Assault on the Tower' are so full of action and excitement that they transcend the Xmas atmosphere.
Varese released the score back in 2003, but it had terrible sound quality and was not complete. The 2011 La-La Land Records re-release expands on Varese's effort and massively improves the sound and presentation. It is a limited edition and out of print, but well worth the money if you can find it.