A 1973 performance of his 1926 piano quartet in D minor op.29 (I don't see any commercial recordings) was on Swedish Radio P2 on Monday (and can probably still be heard until May 15 or so). (see P2 (http://sverigesradio.se/sida/artikel.aspx?programid=2480&artikel=5063153). Carin Gille-Rybrant, piano, Emil Dekov, violin, Åke Arvinder, viola and Lübomir Dragov, cello as noted. Going to go listen now :) )
Sorry, I meant May 15th. (Posted this in April, February 15 didn't make any sense... still, yes, it's no longer available now on May 16th...)