Which of the following is NOT a type of scale in music?

The choice indicating "Fluctuating scale" is correct as it is not recognized as a standard type of scale in music. Scales are essential constructs in music theory that provide the foundation for melody and harmony. The major scale and minor scale are two of the most fundamental types of scales, characterized by specific sequences of whole and half steps that define the emotional quality of the music.

The harmonic scale, while less commonly referenced than the major and minor scales, pertains to a specific variation of the natural minor scale that raises the seventh note to create a leading tone, enhancing its harmonic function. This scale is integral in various musical contexts, particularly in creating tension and resolution in the harmonic progression.

In contrast, the term "fluctuating scale" does not align with established musical terminology, making it an invalid option when identifying types of musical scales. Understanding the primary scales and their variants is crucial for anyone studying music concepts as they form the basis for much of Western music theory and practice.