So, for example, tone is an objective trait, to the extent it is just a sound wave pattern. Similarly, melody is also an objective trait, to the extent it can be notated. Although they agreed on the evaluation of the traits themselves, they disagreed on their relative weighting, and hence disagreed on the overall assessment. That is a subjective determination. And whether or not conveying a particular emotion or not is even important, that is yet another subjective determination.
Originality is harder to pin down.
It is kind of a meta-trait. Objective comparisons can be made to find correlations in the sound wave patterns, note choices, emotional intent, or other traits. But determining which of those correlations are significant, that is subjective. Attaching value to them is subjective. Not regarding the value of traits, but in recognizing the traits themselves.