In addition to scoring the game , the music was used for promotional advertisements and trailers preceding Halo 3 's release .
The score made extensive use of the piano , an instrument which O'Donnell used extensively for composition but which had not been featured in previous Halo music .
In addition to scoring the game , the music was used for promotional advertisements and trailers preceding Halo   's release .
The score made extensive use of the piano , an instrument which O'Donnell used extensively for composition but which had not been featured in previous Halo music .