If I need audio that isn't linked to something I am playing in the OLP service I just play it with VLC. I make my OLP window a little narrower and put a VLC window on the right side of it. That way I can see both OLP and VLC and switch between applications as needed.
Background - We used to use MediaShout which had a built in audio player. If we were doing a drama that had sound effects we would just use that audio player. When we switched to OLP we used the above configuration to accomplish the same thing.