What renders a qirāʾah (Quranic reading tradition) sound, and what renders it šāḏḏ (anomalous). The Islamic science of qirāʾāt has had a clear answer

What renders a qirāʾah (Quranic reading tradition) sound, and what renders it šāḏḏ (anomalous). The Islamic science of qirāʾāt has had a clear answer