Now, I'm pretty good at catching on to the rhythms used in Bulgarian music—having danced for many years certainly helps, but even before that I understood music, including rhythms, pretty well.

Ihtiman, Sofia region, BulgariaBut sometimes the rhythm is really—well, "blurry" is the word that comes to mind, indistinct.  It's there, but it's not very sharply executed.  This happens particularly when the singers are sitting still while they are singing, not dancing.  On my 1980-81 field trip I encountered such a song.  This was in the town of Íhtiman (south-east of Sófia, on the way to Plóvdiv), where I recorded a group of women born in Belítsa (a tiny village about 10 km. to the north-east) but married into, and living in, Íhtiman.  Listen to it:

Един Димитър на майкя (Edin Dimitâr na majkja) (see text below)

What do YOU think?  (See answer, below second version.)  At first it seemed very even, but there was just a little something that left me wondering.  I puzzled over this for years, sometimes playing it for our folkdance gurus and asking what they thought, but no one was sure.
Then in 1985 I was able to go back to Ihtiman and meet with the same group of ladies.  "What dance do you do to that song?" I asked them.  They started singing AND dancing, and immediately the rhythm was obvious, though still not sharply delineated.  Listen again, especially you dancers—I think it's clearer when they're dancing while singing:

Един Димитър на майкя (Edin Dimitâr na majkja), sung while actually dancing

Now, after I started writing this post I got cold feet: I wasn't sure if it really is clearer without the visual element, or not.  So I asked people to tell me what they thought (see comments below), as a way test my own theory.  The general consensus seems to be that neither version is really clear, but the "while dancing" one is a little clearer, if only because there is no pause between verses, as there is in the first version.

The answer?

Thanks to everyone who replied for the interesting discussion.  Catherine and Dan nailed it: it's a gánkino!  But in fairness to people who gave different answers, the singing does leave itself open to being interpreted as a devetórka.  I will add the text, because it really is fun to both sing AND dance this, in the old tradition of "хоро на песен" ('horó na pésen', or 'dance to singing'), where marriageable girls led the dancing until later in the evening when the men with instruments arrived.

If you like these rhythm-puzzles, I have one more I can post that is still un-solved, and many examples of kópanica where the 3rd beat is seriously truncated (sounds like 2+2+2+4, rather than 2+2+3+[2+2]), even when they're singing while dancing.

Song text

Ihtiman 1980:14 Jedin Dimit'r na majkja
Ihtiman 1980:114 Jedin Dimitar na majkja