How do I play a sound only to one specific player once they pass a trigger?

I understand that you can have a set position in the map that plays a sound or music, but the volume can increase and decrease based on the distance the player is from the source.

How would I go about just playing a sound to a select player, so (for example) players could choose some sort of humble tune to have playing in the background, but that other players cannot hear?

Thanks in advance.