Patrick-Costello, thanks for posting that link to the video about the gimbri.   

As a result of checking out that link, I found this video:

mahmoud gunia sur 2M GnAwA

I watched a couple more videos of that music and then went to this Wikipedia page http://en.wikipedia.org/wiki/Gnawa_music for some background on gnawa music {which I hadn't heard or heard of before seeing those videos}.

Here's an excerpt from that Wikipedia page:

"Gnawa music is a mixture of African, Berber, and Arabic religious songs and rhythms. It combines music and acrobatic dancing. The music is both a prayer and a celebration of life. Though many of the influences that formed this music can be traced to sub-Saharan Africa, and specifically, the Western Sahel, its practice is concentrated in north Africa, mainly Morocco and Algeria. (See Gnawa for more details)...

The melodic language of the stringed instrument is closely related to their vocal music and to their speech patterns, as is the case in much African music. It is a language that emphasizes on the tonic and fifth, with quavering pitch-play, especially pitch-flattening, around the third, the fifth, and sometimes the seventh. This is the language of the blues. Ó Gnawa have venerable stringed-instrument traditions involving both bowed lutes like the gogo and plucked lutes like the gimbri (Ar. 쳌äÈÑí; also called hajhuj, Ar. åÌåæÌ or "sentir" Ar. ÓäÊíÑ), a three-stringed bass instrument. The Gnawa also use large drums called tbel (Ar. ØÈá ) and krakebs large iron castanets; Ar. ÞÑÇÞÈ) in their ritual music. The Gnawa hajhuj has strong historical and musical links to West African lutes like the Hausa halam, a direct ancestor of the banjo.

Gnawa hajhuj players use a technique which 19th century American minstrel banjo instruction manuals identify as "brushless drop-thumb frailing". The "brushless" part means the fingers do not brush several strings at once to make chords. Instead, the thumb drops repeatedly in a hypnotically rhythmic pattern against the freely-vibrating bass string producing a throbbing drone, while the first two or three fingers of the same (right) hand pick out, often percussive patterns in a drum-like, almost telegraphic manner."