What is a guembri, the Gnawa bass lute?

The first time I heard a guembri properly, I was sitting cross-legged on a rug in a small Essaouira riad, and the sound came up through the floor before it reached my ears. It is a three-stringed bass lute — a long neck pushed into a hollow rectangular body carved from a single block of wood, the top stretched over with camel or goat skin. The player, a maalem (master), plucks the gut strings with calloused fingers while the heel of his hand thumps the skin, so it is bass and drum at once.

The sound is deep, round and hypnotic, more felt than heard. There are no frets, so the maalem slides between notes, bending them into that loose, swinging groove that makes Gnawa music feel both ancient and oddly funky. A small metal rattle called a sersel sits on the end of the neck and buzzes against the strings, adding a silvery shimmer over the bottom-heavy pulse. Once it locks into a repeating phrase, it does not really stop — it loops you into a trance.

You hear the guembri most powerfully during a lila, the all-night Gnawa healing ceremony, where it leads dancers through different spirits and colours. But you do not need an invitation to a private lila to experience it. In Essaouira, especially around the June Gnaoua festival, maalems play in squares, cafes and riads, and shopkeepers in the medina will happily pull one down off the wall and play a few bars for you.

When I plan a trip for travellers who care about music, I always route them through Essaouira and Marrakech, where the living Gnawa tradition is strongest. Hearing a guembri up close, in the city where its descendants from sub-Saharan Africa first settled, is one of those Moroccan moments that rearranges something inside you. It is the heartbeat of the whole genre, and once you have felt it, you recognise it everywhere.