Music has the ability to take you to the plane from which it comes out. For instance, if a singer is singing from lust, it will push you to the space of lust. If a singer is singing from fear, it will take you to the release of adrenaline. If a singer is singing from love, it will take you to the space of love.
When we sing from the space of Advaita (Oneness), everyone who listens to the music experiences Advaita. Kirtan is a powerful tool to experience Advaita, oneness and completion.