Keino Swamber of the Express recently wrote a story about the Plymouth Jazz Festival, saying it's been hailed by Forbes 500 as "The third biggest event on Planet Earth".
It's actually Forbes Traveller, and here's the site that has a slide show on what's considered the best music festivals in the world.
http://www.forbestraveler.com/luxury/music-festivals-slide-1.html
Of the Plymouth Jazz Festival it says: "Stevie Wonder performed at the first edition of this festival, now one of the Caribbean’s best in terms of both mood and music, in 2005. The repertoire ranges from late model reggae and soca, to classic R&B and funk."
The other festivals include those of the Isle of Wight (England), Fez Festival of World Sacred Music (Morocco), Tamworth County Music Festival (Australia), Salzburg Festival (Austria), and the Sauti za Busara Swahili Music Festival (Zanzibar).