Particular music from gurren lagann ***possible spoilers

i just finished watching the series, i was particularly intrigued by a particular track from the last episode(# 27) of the series, it starts at 1:00 and ends around 3:00, basically the track when they transforms and announce themselves as "tengen toppa gurren lagann"
i downloaded the soundtrack but its not on there, i hope someone out there can tell me where i can find it! :)