how to trigger a song for the player

// This is a public variable so you have to assign the audio clip you wish to play in the Inspector
    var HaloTheme : AudioClip;

    // Make a box, delete the mesh renderer, and make the Box Collider a trigger by selecting 'Is Trigger'
    // Then expand it to enclose the whole area you wish it to cover, ie a room.
    function OnTriggerEnter (other : Collider) {
    // Make sure your character is tagged 'player'
    if (other.gameObject.tag == "player") {

    // Plays the audio that you want...
            audio.Play(HaloTheme);
        }
    }

    // Simply makes it so the object can play audio
    @script RequireComponent(AudioSource) 

Also, i didn't put a comment in there for it, but on the Audio Source comopnet that is added, make sure you have it set to Loop, if you want it to loop that is.