It's a half hour of instrumental PotO songs all blended together... and it is amazing. It's so beautiful - reminiscent of both the stage and movie versions. It's utterly stunning, and I've had it on repeat since I found it last night! And I still get really teary-eyed every single time I hear certain parts... for example, the PonR/final lair section is so overwhelming. It starts out with PonR then blends into final lair, and it is just awesome. And I've never cried at All I Ask of You, but I do with this! I think because it reminds be of the end where Christine leaves Erik and they have the instrumental AIAOY in the background... *dabs at eyes* I'll shut up now, but you'll see what I mean!
You can find more information about it here. Enjoy!
Note: It's in a zip file, and may take a while to download - but it is so worth it.