He was a serious left winger, and someone posted an MP3 of "The Internationale" that was his favorite. I downloaded it and loved it too! It sounded very klezmer, but I couldn't pick out the language, and there wasn't any artist info in the file.
I was reminded of it the other day by seeing this huge collection of versions of the Internationale in 20 languages, so I went on a search for "klezmer Internationale".
Found it! It is, of course a Japanese Klezmer Internationale done by a group called Soul Flower Mononoke Summit, from their album "Levelers Ching Dong". And it's on that big page, too, as I noticed when I went back to see if the Internationale collector had it.
So anyway that's my Obscure Japanese Communist Klezmer-Ish Folk Music story for the day.