Vox Maris is the name of the most well known instrument Hey Organ Builders has constructed. She was built for the Expo 2012 in Yeosu, Korea, and with a volume of 138,4 dB set the Guinness world record as the loudest organ in the world at the Open Day in Urspringen, 21. October 2011. The organ has 80 pipes, up to 10 Meters long, and is a marvel of construction and technology. To devise and build an open-air organ that can withstand wind and weather, stay in tune through any temperature changes that may take place, that can be heard throughout the Expo grounds, can be played dynamically and last not least be played from a tablet PC or other mobile device begs to have completely new technologies invented to fulfill these requirements. So the pipes of the Vox Maris were developed from principles of the Steam Whistle (Calliope) and through their 360 degree Labium develop an impressive volume that diffuses in all directions. The pressure required to bring these pipes to life is about 1,000 times greater than your average church organ, and the system produces a staggering 20,000 liters of  compressed air every minute. One of the highlights of the Expo is that Vox Maris can be heard more than six kilometers away, and yet with reduced pressure is able to be played in harmony with other instruments directly at the Sky Towers during a concert.