Brainwave entrainment, or brainwave synchronization, is a method of applying a periodic aural or visual stimulus in order to convince one's brainwaves to operate at a desired frequency.  This can be especially useful for tricking your brain into waking up or sleeping.  Anabubula has an example sound file that's meant to be a "coffee replacement" for waking up in the morning.  Somewhere around minute 17 or 18, my heart almost popped out of my chest. #science