Ok, I know thie is very late but, way beack before Mothership Zeta was released I remember a topic on what people thought the music would be like in Mothership Zeta.
It got me thinking at the time and I went off and started composing my own themed piece of 'ambient' type music that I thought would fit the game.

Just thought I'd finally show people and see what you guys think, bearing in mind it probably seems a bit un-suitable after playing the actual DLC, I also tried to fit a 'calm' ambience and a n almost 'battle' like part just to give an idea.

Just don't be expecting a John Williams masterpiece or anything! lol.

Here's the link:

http://youtu.be/NA5goACtJb8

It was nice but as you said: No masterpice