DRMAX Dance Dance Revolution 6thMix is the 6th game in the Dance Dance Revolution series of music video games. It was released in the arcades by Konami on October 19, 2001. Although only officially released in Japan, arcade units exist worldwide. 6thMix contains a total of 42 songs, 36 of which are new to Dance Dance Revolution. It was the first in the series to feature Freeze Arrows. In the proto version of this game, it has some songs from DDR 1st-5th Mix.
Source: Wikipedia, "DDRMAX Dance Dance Revolution 6thMix", available under the CC-BY-SA License.