A trick that you may use to make it seem that a tram is moving by with a sound... It cant be like a song, but you may make A BUNCH OF CORNERS, with ambient_generics at each one. As the tram goes, it runs over each corner activating an ambient_generic. As it moves to the next corner, it hits a multi_manager which turns off the last ambient, and turns on a new one. You would keep the sound radius to like small or medium. It cant be like a song, because that would just keep goin.. But if you can find a VERY short ambient sound, that has about the time between your corners, than that would work.. (if you try, and it suck, dont blame me.. I was just thinking "out there")