modesIonian

Ionian is one of the seven modes of the diatonic scale and the modern equivalent of the major scale. It begins on the tonic of a diatonic collection and follows the interval sequence: whole, whole, half, whole, whole, half, whole. Because of this pattern, the mode sounds bright and stable, and it serves as the primary basis for most major-key music.

Construction and examples: The Ionian mode on C yields C D E F G A B C. On G, it yields G A B C D E F# G. In practice, Ionian corresponds to the major key built on the same tonic; the same pitch collection is described by the key signature of the related major key (for example, G major has one sharp to accommodate the F# that appears in the G Ionian mode).

Harmony and chords: When harmonized in tertian chords, the Ionian scale produces a I major triad, II minor, III minor, IV major, V major, VI minor, and VII diminished. Seventh chords built on these degrees yield Imaj7, ii7, iii7, IVmaj7, V7, vi7, and vii°7, reflecting the typical major-key harmony associated with this mode.

Relation to keys and modes: Ionian is the default tonal center for many Western pieces and is used across classical, jazz, and popular music. It differs from other modes primarily by its major third interval from the tonic, which gives it a brighter mood compared to modes like Dorian or Aeolian.

History and naming: The term Ionian comes from medieval and Renaissance theory when the diatonic modes were catalogued and linked to ancient Greek modes. In modern theory, Ionian is seen as the major scale, and its functional role is as the primary mode for major-key music.