What mode is equivalent to a major scale with a raised fourth step?

The mode that is equivalent to a major scale with a raised fourth step is indeed the Lydian mode. The Lydian mode is derived from the major scale, but it features a distinctive characteristic: the fourth degree of the scale is augmented.

To understand this better, let's take a look at a major scale, which consists of the following intervals: whole, whole, half, whole, whole, whole, half. When you raise the fourth degree of this scale, you create the Lydian mode. For example, if we consider the C major scale (C, D, E, F, G, A, B), raising the fourth note (which is F) to F# gives us the C Lydian scale: C, D, E, F#, G, A, B.

This alteration creates a bright and uplifting sound characteristic of the Lydian mode, which is often used in various musical genres to evoke a sense of whimsy or freedom.

The other modes listed, such as Dorian, Mixolydian, and Phrygian, do not feature a raised fourth step. Instead, each of these modes has its unique interval structure that defines the sound and feel of the scale. Thus