Tonality is a musical system that arranges pitches or chords to induce a hierarchy of perceived relations, stabilities, and attractions. The pitch or triadic chord with the greatest stability is called the tonic, and the root (music) of the tonic chord is considered to be the key of a piece or song. Thus a piece in which the tonic chord is C major is said to be "in the key of C". The most common use of the term ..."is to designate the arrangement of musical phenomena around a referential tonic in European music from about 1600 to about 1910" (Hyer 2001). Contemporary classical music from 1910 to the 2000s may practice or avoid any sort of tonality—but harmony in almost all Western popular music remains tonal. Harmony in jazz music includes many, if not all, tonal characteristics, while having different properties from common-practice classical music.