The Ionian scale is one of the seven musical modes and is identical to the major scale. It's one of the most commonly used scales in Western music and serves as the foundation for many musical forms, including classical, pop, rock, and jazz.

Construction:

The Ionian scale is built using the following interval pattern:

• Whole step

• Whole step

• Half step

• Whole step

• Whole step

• Whole step

• Half step

In C Major, it would be:

• C (root)

• D (whole step)

• E (whole step)

• F (half step)

• G (whole step)

• A (whole step)

• B (whole step)

• C (octave)

Features:

• Major tonality: The Ionian mode has a bright and happy sound, characteristic of major scales.

• Stable and consonant: The intervals within the Ionian scale create a stable and consonant sound, making it suitable for creating a sense of resolution and balance.

Chord Construction:

• Tonic chord (I): C major (C, E, G)

• Supertonic chord (ii): D minor (D, F, A)

• Mediant chord (iii): E minor (E, G, B)

• Subdominant chord (IV): F major (F, A, C)

• Dominant chord (V): G major (G, B, D)

• Submediant chord (vi): A minor (A, C, E)

• Leading tone chord (vii°): B diminished (B, D, F)

Usage:

The Ionian scale is fundamental in Western music theory and practice. It’s used extensively in melodies, harmonies, and chord progressions in many genres, providing a strong sense of resolution and tonal stability.