What is it called for a C minor scale in a C major scale
In a C major scale, the C minor scale is referred to as the parallel minor scale.
When a C minor scale is played within a C major scale, it is called "modal interchange" or "modal mixture." Specifically, the C minor scale is borrowed from the parallel minor key (the key of C minor) while the overall tonality remains in C major. This creates a temporary change in the tonal color, adding a touch of the minor mode within the major context.
To determine the name of a C minor scale in the key of C major, we need to identify the relationship between these two scales. In music theory, we use relative keys to describe this relationship.
The relative minor key of a major key is the key that shares the same key signature but starts on the sixth degree of the major scale. In the case of C major, the sixth degree is A. Therefore, the relative minor key of C major is A minor.
So, if we want to find the equivalent C minor scale in the key of C major, we look for the relative minor key, which is A minor. A natural minor scale starting on A contains the same pitches as the C minor scale. Thus, the C minor scale in the key of C major is referred to as the relative minor scale, or the Aeolian mode, starting on the sixth degree of the C major scale.