how can i play different songs in one level? say for example; one song plays outside then you enter a building the song changes to another?
You can check for a character entering an area using a trigger collider (this is just an ordinary collider object with the Is Trigger option enabled). A trigger reports when an object enters it using the OnTriggerEnter function. This function can then call audio.PlayOneShot to actually start the new audio. There is a corresponding OnTriggerExit function which you can use to set the music back to what it was.