In this episode of Once Upon a Sound, Jimmy, a part-time DJ and full-time music geek, and Skip, a professional question-asker and sailing aficionado, travel to Croatia drawn by the never-ending melody of Zadar’s coast. Their mission is to find Nicola Basic, the genius architect who apparently vanished after designing the instrument. Only he can help them unveil the mysteries of the Sea Organ.

To assist in their quest, Jimmy and Skip rally the fifth-generation heir to a family of organ makers, a sagacious scholar of hydraulic engineering, and Croatia’s most-respected music producer. This is an adventure of epic winds, conflicting soccer fandoms, remote islands frozen in time, unnerving boat rides, and a myriad of evocative sounds as old and venerable as the Mediterranean Sea.