I learned about Sixto, about 8 years ago, when a friend encouraged me to watch the Oscar winner documentary about his life. His is a very unique story, he was very popular with young South Africans and became a symbol for the South African Apartheid movement which he never knew until he was in his sixties. No one had ever seen him and his life was a mystery as rumors that he committed suicide on stage were all over the country.
Finally after several research years by a music store owner in Cape Town, they found him, and that's where everything re-started.
Here's the movie trailer
You can still find the full movie on youtube if you search under "Searching for Sugar Man"
There is also an open Spanish version in the RTVE (Spanish Television) website
I encourage you to watch the documentary, as it is an incredible story. You can also find most of his songs on youtube or his official webpage
You can watch on this youtube link "I Wonder" song with the starting bass sound, in the original concert in South Africa for the first time.
Rest in Peace.