The North Sea Jazz Festival, Den Haag, The Netherlands. The North Sea Jazz Festival is the largest indoor music festival in the world, known globally as the event where the past, present and future of jazz are featured within three days. Next to a firm base of jazz as the festivalâs staple music genre, many others, such as blues, soul, funk, or hip hop, pass by. In 1979, American singer Ella Fitzgerald gave an unforgettable performance at the North Sea Jazz Festival in The Hague. Fitzgerald, who was noted for her purity of tone, phrasing, "horn-like" improvisational ability and tremendous work ethic, had recorded a live album with the Count Basie Orchestra at the Montreux Jazz Festival the night before. On the program are a number of songs she rarely performed, such as Make Me Rainbows, Some Other Spring, Dindi, and Theme from Love Boat.