On assignment in Morocco last year, Lonely Planet gave me the task of investigating Sufism, the mystical branch of Islam, for broadcast on National Geographic Channels International. The following footage wound up on the cutting room floor, but recently reappeared on YouTube.

Sufi music is a means of connecting to the Divine through chanting and dance. But it’s more than simply worship; it also serves a therapeutic purpose. When someone is depressed or otherwise mentally ill, Sufis consider the sufferer to be endiablé – inhabited by a devil – and the only solution is to drive away the demon with an ever-crescendoing swell of heavy percussion and songs set to religious poetry. It’s incredibly loud – especially when the horns blare.

Imagine yourself depressed. A brotherhood of ten robed mystics shows up at your bedside and starts drumming and singing in a clamorous fortissimo. There’s no ignoring them – and that’s the point: to penetrate the sufferer’s consciousness, rouse him from torpor, and get him up and moving in a sort of trance-dance. Once this happens, the music must not stop until the endiablé falls to the floor, an indication that the demon has been exorcised.

I must say, it works. Before I arrived in Morocco, all I knew of Sufism was that it’s the mystical branch of Islam. Religious-poetry and musical scholar Youssef Ghazale invited me to experience a house blessing by a brotherhood of Sufi musicians. This was my first major assignment on the first full day of shooting. Frankly, I was freaking out, fearing myself caught in something way beyond my abilities, and I had no clue how to approach the task before me.

The drumming and chanting began. So great was the intensity of noise that my chair shook. I locked my jaw in a frozen smile, but incense kept tickling my nose, forcing me to relax my facial muscles. As the music volume swelled, so did my mind-chatter, and suddenly I was faced with a choice: trip on my own self-made insanity or surrender to the present moment. The horns blasted in a deafening roar, and up I leapt, clapping and hollering alongside the women. By the end, I felt positively giddy.

Up until recently there were few – if any – opportunities for outsiders to hear these glorious, cathartic sounds in person. But lately you can, if you time your trip to coincide with the Fès Festival of World Sacred Music. Be sure to bring your demons with you.