Balalaika. A popular folk instrument in Russia at least as far back as the late 1600s is the balalaika. They tend to have two to six (but usually three) strings, a triangular body, and a short stem. It likely evolved from the Mongolian Dombra, which had an oval body and longer stem, that was introduced to Russia during the Mongol occupation. Nowadays only professional musicians in Russian folk music ensembles and folk instrument orchestras play the balalaika.