What is meant by "laws of melody" mentioned in the context of voice improvement with the Quran, and are the musical مقامات (Maqamat) with their four conditions permissible (halal)?

Scholars have differed regarding the rules of melodic recitation (naghām) in the Qur'an. A group of them preferred permissibility so long as no alteration of letters occurs through prolongation (tamṭīṭ). However, if prolongation leads to distortion and alteration of the Qur'an, such that a letter is added or removed, then it is forbidden. They agreed on the desirability and recommendation of beautifying one's voice when reciting the Qur'an and chanting it melodiously, as long as this does not lead to altering its wording or adding letters to it. Ibn al-Qayyim elaborated that if melodic recitation and chanting (taṭrīb and taghannī) are natural and without affectation, then they are permissible, and this is what the predecessors used to do and listen to. However, if it is a craft that requires effort, artificiality, and practice, like the tunes of songs, then these are what the predecessors disliked and censured.