Victor N Kumok (<vkumok@rambler.ru>), Moscow, writes:

On my info he was
Polish Jew born in Polen or in Belarus. In 1937 he emigrated to
Argentine. I do not know if he died there. I wonder how the Chechs
cannot tell the biografy of that composer. I collect materials about
Kumoks worldwide and if you will have most detailed knowledge on
Josef, Jan or Jorge Kumok (Kumock) I ask you to tell me.