In my Ukrainian church, all panachydas/funerals I've been to during the Paschal Season sing Christos Voskrec! Christ is Risen!
St. Thomas Sunday (next Sunday) we all head for the cemeteries to have little panachydas performed at the graves of our loved ones. At the particular cemetery I visit, the back section is mostly Orthodox - Ukrainians, Russians, Serbs, Belorussians, etc....and the whole place joyfully reverberates with Christos Voskrec!
That's what I thought. We don't intone in the funereal melodies either, it is a joyous season! Perhaps it is a Russian tradition?