In music, a scale is a group of musical notes that provies material for part or all of a musical work. Scales are ordered in pitch or pitch class, with their ordering providing a measure of musical distance. Scales differ from modes in that scales do not have a primary or "tonic" note. Thus a single scale can have many different modes, depending on which of its notes is chosen as primary. The distance between two successive notes in a scale is called a "scale step." Composers often transform musical patterns by moving every note in the pattern by a constant number of scale steps: thus, in the C major scale, the pattern C-D-E might be shifted up a single scale step to become D-E-F. This process is called scalar transposition. Since the steps of a scale can have various sizes, this process introduces subtle melodic and harmonic variation into the music. This variation is what gives scalar music much of its complexity.