Every year in June, thousands upon thousands of tourists from around the world and Moroccans from all over the country flock to Essaouira, a small coastal city about 200 kilometers from bustling Marrakesh, for the annual Festival  of Gnaoua  and world music. The town, made famous by the Rolling Stones and Jimi Hendrix (Castles in the Sand is rumored to have been written about Mogador ), is a year-round hot spot for Moroccan musicians of all kinds, but truly livens up during the festival. This year, many bloggers were in attendance.
The Moroccan Dream explains  a bit of Gnaoua's history:
The Gnawa music inspired a number of great musicians such as Jimmi Hendrix, Led Zeppelin and others. Gnaoua music is a pentatonic music very similar to Blues music because both are rooted in the heart of Africa.
Jimmy Page and Robert Plant went even further to create No Quarter in 1994. No Quarter is a fusion between gnaoua music and rock, following the steps of Randy Weston who was the first musician to fuse his jazz music with gnaoua in the 60's.
Kimany Marley  performs
The View from Fez quotes  festival director Neila Tazi describing the importance of the festival:
We are driven by our passion for music and genuine encounters, our desire to preserve some innocence and dreams in a harsh world. For four days we create a world with values we believe in: simplicity and the basic things in life.
Afropop, a site dedicated to African music worldwide, shared an article  from Dr. Chouki El Hamel, a scholar of African culture, on the cultural history of gnawa and the festival's origins:
Recently, Western musicians interested in African traditional music, have “discovered” the music of the Gnawa. As a result, many collaborations have ensued with famous jazz artists such as Randy Weston. The Gnawa are modernizing their style to make it more secular and with more commercial appeal. With these recent developments and their appeal to tourists, the Moroccan government in 1997established The Gnawa and World Music Festival in Essaouira.
Finally, Agadir Souss shares a video  of the festival:
Photo of Kimany Marley by Agadir Souss .