It can be 2 separate pieces of music. I can very easily crossfade or fade out music so it mixes together.

I"m starting to visualize the video in my head:

Some sort of undefined intro we still need to figure out
We then go to the server browser as we enter a server. Cut to the gameplay footage with kinda slow music, to show the current experience
After a little music either stops, fades out or crossfades into another song. As we launch plus, fade into white with more intense and exciting music as we show some multiplayer footage in plus.
After showing off multiplayer stuff like steaks and spectator, we proceed to show the power of angelscripting.
Then we display the message JJ2 Plus, download today. Obviously I would spice it up more, but my idea on how to do it is REALLY hard to explain in words.

Obviously this is very rough draft, and I may play around in my sony vegas to help get some ideas down.