Which mode is the major scale starting on the do (doh) scale degree?

The major scale starting on the do (doh) scale degree corresponds to the Ionian mode. The Ionian mode is the first mode of the diatonic scale and is defined by its specific series of whole and half steps, arranged in the pattern: whole, whole, half, whole, whole, whole, half. This is the same sequence of intervals that defines the major scale, making it inherently the Ionian mode.

When examining the context of musical modes, each mode has a distinct sound and characteristic formed by the arrangement of those whole and half steps. The Ionian mode, with its bright and stable sound, is what we typically associate with the concept of "major." It serves as the foundation for Western music's tonal framework, making it arguably the most commonly used and recognized scale in music.

The other modes, such as Dorian, Phrygian, and Mixolydian, each start on different degrees of the major scale and have their own unique interval patterns, leading to different tonal qualities and emotional expressions. This distinctive nature of Ionian, aligning it closely with the major scale, confirms that the major scale starting on the do (doh) degree is indeed the Ionian mode.