Throughout the lifespan of the short twentieth century, tidal waves of sounds hitherto unheard of swept through a rapidly globalizing world – disturbing, exciting, and potentially endangering seemingly calm waters. These waves mostly originated in the USA or in Great Britain. Their impact lessened with the distance they crossed, but at least some ripples would reach nearly every corner of the inhabited world. At times, their impact created reverberations, whether in the form of sources incorporating foreign material, or in the form of the original impulse, transforming and flowing back.