Marconi Union is a British musical trio specialising in ambient music, and Weightless was produced in conjunction with the British Academy of Sound Therapy (back in October 2011) to be one of the most relaxing songs ever heard. With guitar, piano and electronic samples of “natural soundscapes”, one would kind of expect it to be somewhat relaxing… but, they were so successful (scientists measured a 65% reduction in anxiety and a 35% reduction in heart rate) that motorists have actually been warned not to listen to this while driving.