With the new audio module it shouldn't be a big thing to handle triggering of sounds using the event manager.
The Engine will not support stopping a soundclip right before or after a down-beat - that's too complicated.
(Instead it will "stall" the soundclip when stop() is called)
In future releases of the audio module it will be possible to apply effects to the soundclips. (such like fade-in/out) But before we get as far as that you're well advised composing with fades.