Tremolo Loon Calls – Tremolo http://www.rennerwrites.com/wp-content/uploads/2015/01/tremolo.mp3 The Tremolo is used when Loons feel threatened and want to sound an alarm. It almost sounds like the Loon is laughing. This is the sound most people hear because Loons will use it when they are approached by a boat or humans. Lonnie the Loon Learns to Call, page 7