Hero Down by Kevin MacLeod
A piece in three or four parts... depending on how you count parts. The penultimate section features a lonely flute, slowly joined by a children's choir, and finally exploding into a giant choral and orchestral ending.
From the original soundtrack to "The Last Stand of the Mechanolith".
This piece of music is available in an uncompressed format here.
This track is amazing! So many feels to it!