Major vs. Melodic Minor

Both of these start on C, and if you only look at the third, they cover the entire distance between major and minor in a single note.

C Major holds a natural third against the tonic - the brighter of the two.Hear C Ionian in the app

C Melodic Minor lowers that third by a semitone, into a minor third.Hear C Melodic Minor in the app

The wheel makes the difference positional rather than verbal: the third-degree wedge sits one wedge further counterclockwise in Melodic Minor, and the spoke drawn from the center recolors to the interval that degree now forms with the tonic. Everything else on the two wheels is identical.

That single note is the cleanest way to describe Melodic Minor there is - not the natural minor scale with two degrees raised, but the major scale with exactly one degree lowered. Every other minor color a scale can have - the flat sixth of harmonic minor, the flat seventh of natural minor - is simply absent here; Melodic Minor keeps the major scale's brighter upper half intact and touches only the third. Reading it is one thing; the difference is much more obvious held under a drone, which is what the links under each figure are for.