Following recent albums by Issa Juma & Super Wanyika and D.O. Misiani & Shirati Jazz, Sterns Africa releases a third CD of classic East African pop music.The Western Jazz Band is one of those names known to hardcore African music fanatics but to no one else outside of Africa (a happenstance that's about to change).  It was one of the most popular groups in Tanzania in the 1960s and '70s.  It took its name from the country's Western Province, where most of its members originated, though they met and formed the group in the coastal city of Dar es Salaam. The term ''jazz'' indicated that this band played modern music for sophisticated city folk; it wasn't jazz in the American sense but guitar-driven dance music that combined Congolese-style rumba rhythms and the breezy, light-hearted Swahili vocals of the coast.  Tanzanians called this style saboso.  Call it whatever you like, it's delightful music that won't remain unfamiliar to Americans once this album gets around.The 17 tracks on this CD, selected and annotated by East African music expert Douglas Paterson, represent the Western Jazz Band at its peak in the 1970s, when these songs rocked the dance clubs of Dar Es Salaam.  They still rock.