Quick history, which might be kind of faulty as I don’t speak Czech: six years ago, jazzy world-music collective Yellow Family was founded in the Czech Republic. A couple of years ago, between gigs, its female vocalists decide to form an a capella side-project quartet called Yellow Sisters to make some extra euros. Now, after finally settling on a permanent lineup, Yellow Sisters is blowing up huge in Eastern Europe. And if there is any justice, Singalana will do the same for them all over the world.

Wait, stop—where are you going? Not enticed by the thought of a Czech female a cappella quartet? Okay, I realize how it sounds, put like that. But it’s not like that at all. First of all, this isn’t some easy-listening soft-soap noodling, here; Yellow Sisters are kind of fierce in their attack. Their roots lie not in Nylons-style cabaret vocalizing, but in world music—they are heavily interested in reggae, which seems to be their default genre. “Bzum” is the only a cappella reggae song about bees I’ve ever heard; the track’s special guest, Gambian singer Papis Nyass—husband of Yellow Sister Antonia—contributes a great toast tying the song’s subject to the whole birds-and-bees thing. And while “Free to Do” rides an unfortunate Bobby McFerrin-type groove, the song’s pretty hooks (and lyrical ambiguity) manage to stave off “Don’t Worry Be Happy” flashbacks. But it’s just a bit too jarring when actual drums come in on “Back to the Roots”—they’re all so good at vocal percussion that this intrusion seems thoroughly unnecessary.

But the group’s scope is a lot wider than just reggae; they’re also interested in West and South African music, as well as South American folk, European art-music, and North American soul and jazz singing. In “Vitr”, all the vocalists cycle through all these styles, sharing lead and background vocals like it ain’t no thing at all. Occasionally, they all erupt into one long-held dramatic and unexpected unison harmony passages, only to drop away again into hide-and-seek fugue parts. About 3/4 of the way through, things shift into a new Steve Reichian rhythmic pattern, which pings and pongs between two different singers, then three, then all. It’s stunning and beautiful, but it is also a lot of fun.

Track after track, Yellow Sisters show what is possible with a little talent and a whole lot of hard work. “Revolution”, sung in English and Spanish as well as Czech, is a showcase for precisely-timed rondo interplay, but it is also furiously emotional about the need for political change. (The drums that bust in at the end turn out to actually be some great beatboxing by someone named Jesus.) “Tapalapa” is as warm and sexy, but the track called “Do Me” is, surprisingly, wry and regretful about how the song’s subject should NOT just “do” its protagonist.

These four young women—Antonia, Léna, Hawa, and Bára—have delivered one of the loveliest and smartest records of the year. In the past, this record might never make it out of the Czech Republic. But now, with this new Internet deal they’ve invented, one can get the whole thing on MP3 with just a few clicks and a credit card. Pretty cool world we live in, huh?

• "Tapalapa" MP3