Disquiet

Face is Disc 1, Track 17 on the Xenoblade Original Soundtrack. It plays during these cutscenes:
 * Shulk's vision of Reyn being attacked by the in Tephra Cave
 * Shulk, Reyn and Sharla noticing the Mechon in the Ether Mine
 * Alvis watching Ahulk and Reyn depart from the distance at the Lakeside in Makna Forest
 * After Shulk's vision of Melia being attacked in the High Entia Tomb at the Centre Gate in Eryth Sea
 * When Junks arrives at the Ventilation Conduit in the Central Factory
 * The party finds Tyrea unconscious outside of Colony 6 during the Melancholy Tyrea