In a fascinating post at the New Yorker's Goings On blog, Alex Ross describes how music has been used as a means of psychological warfare and torture from World War II to the present. A few examples:
At the end of 1989, when Manuel Noriega was barricaded inside the Papal Nuncio's residence in Panama City, American troops set up loudspeakers and subjected him to an unending stream of rock music, with a playlist favoring heavy metal. In 1993, during the siege of the Branch Davidian compound in Waco, Texas, the F.B.I. blasted Tibetan chants and other allegedly annoying sounds in an effort to break the will of the cult. The efficacy of these strategies is open to question; in the case of Waco, they were adopted against the advice of negotiators, and may only have hardened the cult's resolve.
Since the beginning of American operations in Afghanistan and Iraq, music has routinely been used during interrogations at Guantánamo and elsewhere. The playing of loud music, customarily hip-hop or heavy metal, is part of a standard procedure that the Department of the Army describes as "futility": "[The] collector convinces the source that resistance to questioning is futile. This engenders a feeling of hopelessness and helplessness on the part of the source."