Infiltrate

200px Infiltrate is a song included in the Halo 3: Original Soundtrack. It plays during the level Sierra 117.

It starts with a low strings note, with drums playing background. High strings play and hold a note, but drums continue to play melody. The song picks up the pace, and louder drums join in. At 1:47, strings begin to play the melody, which is in a minor key but has a hint of major in it. Choir also joins in, but strings and drums still keep the melody, which alternates between major and minor. This melody continues until the end.

It runs for 3 minutes and 50.06 seconds (3:50.06).

When the bass begins followed by the three percussive sounds, seven such percussion sets follow before the percussion suddenly becomes high-pitched and then returns to normal. This is another 7 reference. Strangely enough, it never happens again in the song.