http://www.maurograz...Acustica04.html
The interval covered by a critical band is about 1/3 of an octave.
Meanwhile, note that the tone and therefore also the semitone are always within the critical band. This explains why major and minor 2nd dyads always give a harsh sensation. It also explains why in "clusters" of semitones and tones (cluster = chord formed by various notes at a distance of a semitone or tone) individual sounds cannot be distinguished, whereas they are clearly distinguishable in an chord of superimposed thirds.
Note also that in the lower part of the sound spectrum, the critical band is a bit wider, enough to include even the minor 3rd (and in the very low part, even the major 3rd). This explains why, in the bass, a 3rd dyad sounds bad and also why, in the practice of counterpoint, a certain space is always left between the bass and the other voices.
Reading this article, the rules of part-writing are based on scientific rules. I am not casting doubt ... which is why much music "sounds bad"
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