LawsuitThe NES version of Tetris was available in two different releases, one by Tengen and one by Nintendo. After an extensive legal battle, it was decided Tengen did not have the rights to distribute Tetris for the NES and was ordered to cease distribution of the game. All of the unsold copies are believed to have been destroyed making the Tengen release of Tetris one of the more uncommon NES games.
MusicIt's not uncommon for versions of Tetris to incorporate musical motifs from Russian classical and folk melodies; in most versions, a rendition of Korobeiniki (here present in a somewhat mutated form as Troika) is part of the metric Tetris standard. Sometimes however there is musical padding brought in from other sources. While trying to discern the musical origin of another piece of music here, Bradinsky, I found the answer staring back at me from the credits, in the form of Brad Fuller. (It wouldn't surprise me to find that Loginska, another musical composition in this version, is dedicated to programmer Ed Logg. Finally, Karinka is just a mush-mouthed manhandling of the traditional melody Kalinka.)
Information also contributed by Pseudo_Intellectual