The Ensemble Instrumental National du Mali is not just concerned with instrumental music -- and it's not your typical mild-mannered folkloric group, either.
Rather, since its formation in 1961, the Ensemble has worked to preserve and further world understanding of traditional Malian music. Its albums capture expansive (and extemporaneous) vocal exchanges between an improvising lead singer (here, Djelimadi Sissoko) and the large responding choir. All of the albums available here are transfixing, and though the sound quality of this live video isn't great, it nonetheless offers a nice introduction to this group -- and a sound that clearly inspired such powerful Malian singers as Salif Kieta and Oumou Sangere.
Having trouble embedding the video, so here's the link.