In 1915, when Kodály wrote a substantial Sonata for Solo Cello, Bartók commented: "This is not a mere imitation of Bach's polyphonic style". That was praise in several ways. His friend's sonata had nothing to do with what was old and German, but rather it was contemporary and Hungarian. And it was new.
Kodály was the first person to enhance the cello repertoire with a major solo piece since Bach composed his suites almost two hundred years earlier. He produced an almost incredibly virtuoso sonata and one is tempted to ask why he did not further develop it into a string quartet.