Quite the Vacation Resort
From Halopedia, the Halo wiki
Quite the Vacation Resort is an exclusive song found on the Halo Wars Bonus DVD. It runs for 2 minutes and 7 seconds.
It can be heard in the scene when Professor Anders explains to Captain Cutter that the planet Arcadia was somehow linked to the artifact they found, and when at the same time a distress call was sent to them from Arcadia, requesting military assistance for evacuating civilians.