From Hard Drop Tetris Wiki
Tetris at tetris.com uses three versions of this song.
Traditionally, this song was called Korobeyniki and it is a Russian folk song. Tetris (Game Boy) made this song a part of the Tetris Guideline, and a registered trademark of TTC (77037539). Another name for this song was Korobushka. Korobeiniki is the preferred spelling, used by TTC.