Last century, the Muzak company created custom mixes of soft music for locations ranging from doctor's office waiting rooms and restaurants to barber shops and, yes, elevators. Muzak were self-proclaimed "specialists in the physiological and psychological applications of music." Two decades before Brian Eno riffed on this environmental music concept with his phenomenal "Music for Airports" (below), Muzak provided music for airplanes in the form of reel-to-reel mix tapes played on United Airlines flights. Above is one such collection. Fly the friendly skies.