Habib Koite, a singer and guitar player who lives in Bamako, Mali, in west Africa, will play at the Iron Horse Music Hall on March 21. He will be accompanied by Bamada, his five-member band. Koite (pronounced KWA-tee) possesses an unusually warm voice and guitar skills that inspired Bonnie Raitt to famously tell him after one concert, "I would drink your sweat."