So, I wrote this...
http://soundcloud.com/drdissonance1/nightmare-moon-theme-variation
The opening theme is what you hear when Nightmare Moon shows up in the actual show! The rest is variations of the theme...
So, this is basically a theme and variations on the Nightmare Moon Theme!
It follows Anderson's progressions and such enough, but with the odd change, most notably, emphasizing augmented 5ths whenever I can...

It's a Double Concerto because it's scored for String Orchestra, Solo Cello and Solo Harp (lets pretend it's a Lyre)...so, effectively, it could become a Double Concerto starring Octavia and Lyra! If that was the case, this would be the second movement and I'd have to find more themes from the show to use!
Also, here's a fun story: I've been using Sibelius 6 for 2 years...and Garritan's Personal Orchestra for 2 1/2 years...and only now do I find the vsts titled "Lush *insert string instrument here*" which sound so much nicer in tremolo than normal strings! Lovely!
I also had a look at other vsts around the web and OMG! The Vienna Symphonic Library sounds amazing!

And that's my story...
It's in WiP, because it's probably going to be a movement from a larger work...
Anyway enjoy, I'm going to go drool all over the Vienna Vsts...