What you're training
Mixolydian is major with one note changed — the 7th degree flatted, Bb instead of B in C. Dorian is natural minor with one note changed the other way — the 6th degree raised, F# instead of F in A. Every melody in this drill is stepwise and built to sound that one degree at least twice, so the color isn't hidden in a passing tone — it's the whole point of the phrase.
Two levels, one skill
Level 1 asks major or mixolydian: a short scale-run melody in C, and you catch whether the 7th degree resolved up like a leading tone or sat flat like a bluesy subtonic. Level 2 moves to the minor side: natural minor or dorian in A, listening for whether the 6th degree stayed dark and flat or lifted into dorian's brighter, jazzier color.
Go deeper
This drill is Trio 9 of the ear-training series — modal color heard melodically instead of harmonically. The theory: modal schemas → covers how each mode functions as its own tonal system. For the fundamentals, Modes from the top → walks through all seven diatonic modes and where they come from. The chord-level cousin — parallel-minor loans → is the harmonic version of this same idea, borrowing a whole scale's color instead of reshaping a melodic line.
Where it fits
Comfortable with scale degrees and melodic contour already? Mode color sharpens the same ear for a single altered degree — the skill that lets you hear a melody's mode, not just its key. The full drill ladder has everything else.