A droning vocal line in a low register with bright high notes whiffling in counterpoint, all issuing from the same mouth—this is what you’ll hear from overtone singers in Indigenous cultures across the continents. A perhaps unlikely master of this ancient art is the South African-born Gareth Lubbe, who moonlights (or is it the other way around?) as a world-class violist and member of the string faculty at the Folkwang University of the Arts in Essen, Germany. Listen for Lubbe doubling as narrator and overtone singer in Matthijs van Dijk’s searing Moments In a Life. Scored also for string quintet, clarinet, percussion, and piano, it’s a collage-portrait of the late anti-apartheid activist Dr. Denis Goldberg, who stood trial with Nelson Mandela in the early 1960s and served 22 years of hard time. As such, it brings to a fitting close this season’s Met Orchestra Chamber Ensemble six-concert series at Carnegie Hall’s upstairs chamber venue, Weill Hall. Arguably the Met’s most distinctive legacy of the music directorship of James Levine, these series showcase hand-picked instrumentalists and guest vocalists in programs designed to challenge and stimulate as well as to delight. Thus, two out of four pieces on the present occasion are known favorites by Brahms (Two Songs for Alto, Viola, and Piano, Op. 91) and Ravel (the spicy Chansons madécasses). But alongside the Van Dijk, the bill also includes Bongani Ndodana-Breen’s Rainmaking in Memoriam Queen Modjadji, scored for a singular combo of flute, viola, harp, marimba, and percussion. This concert is one of several Carnegie Hall has bundled in the minifestival “Spotlight on the Music of South Africa” (October 25 to 29).Other headliners include the sensational jazz pianist Nduduzi Makhathini, the genre-defying cellist Abel Selaocoe with his Bantu Ensemble, the star vocalists Zolani Mahola and Jesse Clegg on a “double bill,” and the explosive Ndlovu Youth Choir. The Ndlovu, we’re told, is the first choir ever to reach the finals of America’s Got Talent. Africa’s got talent, too. —Matthew Gurewitsch