I FOUND IT.
By a very circuitous route - we happened to watch Kill Bill Vol. 1 earlier, and the music behind the sword-making scene was "The Last Shepherd" by a pan-flutist named Zamfir. I said to Paul that the music on the animation was a lot like it, and then it twigged it might even be the music.
So I went to Amazon and found the soundtrack, then stuck the track name into Google, which took me to Wikipedia, which took me to Zamfir's credits on IMDb, where I had a total EUREKA moment and found the bloody short film, which is called Paradise. It's not all on a black background as I remembered, but it EXISTS, which means I'm not insane or delusional. :D