How can the Lydian mode be characterized in terms of half steps?

The Lydian mode is characterized by its unique sequence of whole and half steps, setting it apart from other modes in terms of its interval structure. In the Lydian mode, the interval pattern consists of major whole steps between most of the degrees, except for a distinctive half step that occurs between the fourth and fifth degrees, as well as between the seventh and eighth degrees (which is the octave).

When assessing the correct choice, the identification of half steps occurring between the fourth and fifth notes of the scale, as well as between the seventh and eighth notes, accurately reflects the Lydian mode's interval characteristics. This distinctive half step between the fourth and fifth degrees is what gives the Lydian mode its bright, raised fourth sound, which plays a crucial role in its harmonic and melodic qualities.

The understanding of how half steps function within the context of the Lydian mode is fundamental for distinguishing it from other modes such as Ionian (major) or Mixolydian, where the placement of half steps varies. In this case, the presence of half steps in the specified positions further reinforces the identification of the Lydian mode's structure, making the correct choice informative for recognizing this particular mode.