Every now and then I listen to a song and think of all the musicians who have called world music a ghetto, complaining that it prevents them from being evaluated as they deserve. I thought of it again during The Rough Guide to the Music of Tanzania as I was listening to Nia Safi and Imani Ngoma Group. Their “Kibati” demonstrates the kind of motley inventiveness that would have scores of Western reviewers nodding in appreciation if they were, say, an English-language indiepop collective. They’d be described as “folk meets electricity meets rap meets Brazil meets seagull sound effects,” or “an acoustic version of an electronic mix” or simply, “engagingly weird.” “Kibati” takes traditional Zanzibarian music and integrates it with Brazilian whoops and whistles alongside samples of seaside noises that have no real reason to be there but somehow make the song just that little bit more defiantly odd.

So, lets’ say we do the Nia Safis of this world a favour. We take the World Music sign from the music store and throw it away and then we file “Kibati” under Alternative. Now where do we put the other songs from this disc? Werner Graebner has given us a balanced spread of Tanzanian music, with musicians ranging from Dataz, who only recently got out of high school, to the Ikhwana Safaa Musical Club, who last year celebrated the one hundredth anniversary of their founding. Where are they going to go?

There isn’t a separate section of our store set aside for Afro-Cuban Dance Bands, so Mlimani Park Orchestra, OTTU Jazz Band, and Vijana Jazz Band will have to be filed under Popular, along with the other decades-old acts who are still putting out fresh recordings. All three of them are survivors of the 1990s political upheaval that saw the state’s sponsorship of bands come crashing down, making the market freer and more volatile, so we’ll show some respect for their longevity. Paste a quick note over Mlimani Park Orchestra to recommend their lead singer Hassani Bitchuka ‘s evocative falsetto to customers. The man can sob at a high register (it sounds as if he’s responding theatrically to sadness in the lyrics) and that’s worth a listen.

The late Ndala Kasheba and his guitar can join them. He moved over from the Congo in the late ‘60s, and you can hear the influence of Central Africa in the light, resonant precision of his playing. He was part of a band as well, but on this album he’s earnt himself a solo credit.

Dataz and X Plastaz go under hip-hop. If there’s no hip-hop section in our hypothetical store then Dataz, who has a lightness that makes her a little ambiguous, can go under Urban, while X Plastaz can go under Rap. In “Dunia Dudumizi”, this Maasai group set up a call and response pattern between their deep Swahili flow and a sampled yell that swerves back and forth. Unlike most of the musicians on this compilation they have a website of their own, complete with mini biographies. (Did you know that the Godson Rutta was the winner of the 1998 Arusha Mr Retro ‘70s dress competition? Neither did I. The world is full of unexpected things.)

Where would you put Saida Karoli? You’d rank her alongside other female singer-songwriters with distinctive voices, but I’m not sure if that leaves her under Popular or Alternative. The tune of “Omukaile Kilinjwi” is simple and repetitive, and the repetition would pall after a while if she didn’t sing over the top in her breathy, unaffected warble, high and slightly husky and inimitably compelling.

Now for taraab. If I had my druthers then taraab would inhabit a well-stocked category of its own, but it doesn’t, or at least not in my neighbourhood music stores and probably not in any music store outside Tanzania. It’s home region, Zanzibar, is part of the old Indian Ocean trade route and almost entirely Muslim, so the music has a strong Arabic flavour. It’s not a formal sound, but rough-edged and beguiling; heaving and curling along like a sea monster. When you have a full old-style orchestra, as you do here, in Ikhwana Safaa Musical Club’s “Vingaravyo,” then the songs have a grand, go-for-broke quality about them, a wild, almost drunk sound, as if waves are coming in from the sea, snatching up notes, and throwing them at you.

Mohammed Issa Matona’s “Msumeno” taraab is a smoother, more modern piece of music, but I wouldn’t put one track above the other; both are good. Listening to “Msumeno” for the second time, I realised that I had unconsciously begun whistling the tune.

The Master Musicians of Tanzania, who play masses of marimbas, are going to be the odd ones out. They turn out traditional tunes in a clean style that shows college training, so let’s put them under Classical. Classical Percussion, next to Evelyn Glennie. Nothing else is quite right.

To be honest, all of these categories are an awkward fit (with Dataz and X Plastaz as the exceptions) so we might as well shrug and admit defeat and bring back the World Music sign. The songs can stay there until such time as the radio stations start to integrate foreign-language music into their repertoires as a matter of course, or until taraab catches on and gets a sign of its own. Oh, the compilation? It’s excellent. Graebner also co-compiled The Rough Guide to the Music of Kenya, and if you liked that one then you should enjoy Tanzania as well. The music isn’t the same, but the way the playlist is assembled gives it a similar flavour. He has a good ear. For breadth and range and quality, I don’t think there’s another Tanzania sampler out there that could touch it.