In this context, ‘disgust’ doesn’t mean disgusting music… It’s a certain mood evoked by minor tonality, and slightly more energy and less stability than sadness. For example, a lot of late-90s trip-hop falls into this category.
With more energy and less stability, disgust comes across as having more momentum and direction than sadness or despair. In this way, disgust is more ‘active’-sounding, even though it still has mostly low energy overall.
Fear builds on disgust by focussing more on dissonant tonality. The low energy remains, but the instability is ramped up and becomes a prominent feature of the musical texture. While a stable low energy texture can convey calmness and reflection, an unstable low energy texture conveys uncertainty and unease.
Fear can also be used to convey feelings of apprehension. Apprehension is particularly effective when it hints at a previous section of music that was particularly high-energy or even startling.
Aggression takes the minor (or dissonant) tonality and instability of fear, but adds high energy. The high energy works together with instability to add excitement and action to the negative tonality.
Aggression can also be used to convey feelings of anger or violence. It can also be expressed with less stability, but it is less effective. It might be appropriate, however, to express a more stable aggression in a song to contrast with less stable musical textures.