Trace Amounts

Trace Amounts is a song included in the Halo: Original Soundtrack. It plays in the Halo: Combat Evolved Campaign mission The Library. This piece contains electronically generated sounds and a relatively slow tempo. The ominous tone reflects the library's dark past.

The name "trace amounts" is a reference to the effects that the Flood has on an atmosphere, as was said by the monitor of Installation 04, 343 Guilty Spark. Because when scientists refer to the contents of an atmosphere the say, for example, 21% Oxygen, 78% Nitrogen, and "trace amounts" of other gasses.