From 'Exotica. Fabricated soundscapes in a real world' by David Toop:
"Yma Sumac's origins are still in doubt, muddied by claims she was an Incan princess, a descendant of Atahualpa, who was killed by the Spanish in 1527. This dubious legend was matched by counterclaims that she was Amy Camus from Brooklyn. (...)
Only few singers possess the freakish, octave quality of Sumac's voice. (...) A generic jungle landscape is conjured, interspersed with magisterial orchestral climaxes, presumably suggestive of pyramids, citadels and sun temples rising out of forests." (...)
Sumac, like the parabola of her voice - its low moans and masculine gutteral, the musical saw of her upper registers - floats between identities, wrapped in the image manufacturing of Hollywood and her self-created ambiguities."
Below are YouTube videos to the 1954 film 'Secret of the Incas' which stars Sumac.