modus

The term "modus" in music refers to a system of ordering musical notes within a scale, defining the intervals and relationships between them. This system provides a framework for melody and harmony. Historically, this concept evolved from ancient Greek modes, which were believed to have ethical and emotional characteristics.1

In Western music, these modes were adapted into the eight church modes used in plainchant, such as Gregorian chant. These modes, often named after Greek modes like Dorian and Phrygian, are characterized by their specific arrangement of whole and half steps within an octave. Over time, particularly with the development of polyphony and harmony, the church modes gradually gave way to the modern major and minor scales, which form the basis of tonal music. The concept of modes also exists in various non-Western musical traditions, each with its unique scalar and melodic structures.213