The only Sufis I had ever come across before were Dervishes (of the whirling and non-whirling variety) the couple of times I have been to Konya in Turkey. The Essaouira troupe didn't whirl but they represent a long and honourable tradition of blending mysticism with musical virtuosity. The religious and musical heritage is passed on by Sufi Master to pupil across the generations. Particularly poignant was the story from one of the group, the grandson of a slave, about the metal castanet-type instrument he played -- they were apparently representative of the iron shackles his ancestors wore.
I need to learn more about this whole area and am keen to explore links with the Tarab tradition in Zanzibar (of which I feel but don't know, there must be some).