Music can influence our emotions and the quality of our judgements.
Our emotions play a key role in how we reason. If we are emotionally out-of-whack, then we will not be able to reason as effectively. Music is the art form that is most able to dissuade us from thinking critically.
Our brains have a plastic property - the circuits we use more get stronger, those we use less atrophy. The characteristics of the music you listen to; and the way you choose to listen to it will affect your ability to make decisions.
Because of these properties music has always been an attractive vehicle for propaganda. Music's power to persuade is at the heart of Plato's argument for censoring the Arts.
So what gives music this power? Nature built us to look for beauty, and music exploits our tools for finding it.