People have been using music as a means to express dissatisfaction for as long as we know, but why is it so powerful?“I thought that if you had an acoustic guitar, it meant that you were a protest singer,” sang Morrissey on The Smiths’ song “Shakespeare’s Sister.” Back in 1985, that might not have been an unusual point of view. The idea of protest singers as finger-picking folkies had been long cemented in popular culture, going back to the 60s, when Bob Dylan brought songs such as “The Times They Are A-Changin’’ to the masses, spawning countless copyists voicing virtues...