R4.5 includes the way-cool three-dimensional multi-track audio mixer 3dmiX. After you’ve had time to blow your mind suitably with that, take out some time to play with 3dmiX’s About box. Turn your speakers up loud and watch… but don’t just sit there — interact with it. Its behavior is difficult to describe; you just have to mess around.
A couple of undocumented secrets: The Spacebar has an immediate effect on tracer longevity, while the Tab key affects the base pitch of the background sound.