From the Monster Hunter Frontier G3 Preview Site
http://www.mhf-g.jp/preview/g3/
This background music is played on the website, showing the upcoming new Monster for the G3 "Expansion"
Perhaps it is the new Monster's theme(?) I will update title and description when more news is released so it is more properly titled. Anyways, please enjoy
All rights go to Capcom
Wallpaper of the new G3 Monsters Available: http://globalmonsterhunters.tumblr.com/post/60434982542/monster-hunter-frontier-g3-wallpapers-sizes
Edit: Name released on the 12th of Sept 2013. Monster's name is バルラガル (Baruragaru)