Complement (biology) is a group of proteins of the Complement System , found in blood serum which act in concert with Antibodies to achieve the destruction of non-self particles such as foreign blood cells or bacteria.
In traditional Music Theory a Complement (music) is the Interval added to another, that is placed on top of another, so that their complete span is an Octave , while in Musical Set Theory the complement of a pitch class set are those pitches not included (the pitches needed to form an Aggregate ).
