Violists around the world know that, compared to the violin, their solo repertoire is rather limited. That is likely why 20-century violist William Primrose commissioned Béla Bartók (1881–1945) to write him a Viola Concerto in the 1940s. Unfortunately for Primrose, Bartók never got around to finishing the concerto. Leukemia took his life in 1945 leaving two works incomplete – his Third Piano Concerto and the Viola Concerto.
While the Third Piano Concerto was just about complete (the only thing still needing a few tweaks was the final measures of the work), the Viola Concerto was still sketches on manuscript pages without any notes in regards to instrumentation. Bartók composed in ink so the pages were likely difficult to read as he scratched out passages and re-wrote portions.