The Balalaika is a Russian stringed musical instrument. It has a triangular wooden hollow body, fretted neck and three strings. Tuning of the string is in such a way that two of them are tuned to the same note and the third one is in perfect fourth higher. A Fourth is a musical interval with four staff positions in the music notation of Western Culture.
Balailaka is used mainly in the Russian Folk Music and Dances. It is available in different sizes from the highest pitch to the lowest. They are like Piccolo Balalaika, Prima Balalaika, Secunda Balalaika, Alto Balalaika, Bass Balalaika and Contra-Bass Balalaika. The Prima is most common and Piccolo is rare. Prima, Alto and Secunda are played either with fingers or a plectrum pick depending upon the music being played.
Here is a small video on how it is played.