Formed in 1995, Mogwai quickly made a name for itself with adventurous guitar work and a sound that loosened and opened up the imagination. Over the course of the next sixteen years, the Scottish band very much plotted its own course through exploring every sonic whim without losing a strong sense of musical identity. Though often associated with post-rock, Mogwai (due at the Bluebird Theater on Monday, May 2) has always been more of a rock band than that, even though most of its songs are instrumental.