If the adhān is called as a chant, that is, made to be melodious to where it is called with a melody, stretching its letters like that of a song, this is permissible although it is disliked. There is a difference of opinion in this issue. Among the scholars are those who say: The adhān of the one who calls it with intonation is invalid because calling the adhān is a form of worship, and this chanting transforms it to other than that, inclining it closer to that of a type of chant or song.

If it is subsequently called with mispronunciations, contrary to the rules of the Arabic language, then this issue is divided into two categories:

1. That which renders the adhān itself invalid because its meaning has been changed
2. That which does not alter the meaning of the adhān allowing it to remain valid, although it is disliked

For example, if the muʾadhin says: ‘الله أكبار’, (adding a long vowel – alif) this will invalidate the adhān because it changes its meaning. The word ‘أكبار’ is the plural form of the word ‘كَبَر’ which refers to a drumbeat [in Arabic].

If he says: ‘الله وكبر’ it is permissible in Arabic language for any hamzah with a fatḥah that occurs after a ḍammah to change to a ‘و’.

If he says: ‘ أشهد أن محمدًا رسولَ الله’ [with a fatḥah on the word رسولَ], then this is undoubtedly a mispronunciation which alters the meaning according to the most famous dialect. Here, the caller would not have stated the predicate [which must have a ḍammah following the word ‘أن’; leaving the sentence incomplete]. Although, there is another dialect wherein the predicate following ‘أن’ may be manṣūb [accusative, having a fatḥah] so this is acceptable. It is also present in the poetry of ʿUmar ibn Abī Rabīʿah who was from among the most prolific speakers of the Arabic language. In this dialect, reciting the word ‘رسولَ’ manṣūb [with a fatḥah] is not incorrect as long as the caller believes the word to take the place of the predicate following ‘أن’.

If the caller says ‘حيا على الصلاة’ then, according to the most famous dialect any word that is ism fiʿl [word in Arabic that has attributes of both a noun and verb; here the word ’ حي’] is not accepting of added vowels [in Arabic: ا, و, or ي]. Although it is most apparent that this addition does not change the meaning and the adhān called in this way would be deemed valid. This is because the extent of the change is that the fatḥah [on حيَّ] is over-pronounced to where it sounds like an ‘ا’.

Source: Al-Sharḥ al-Mumtiʿ 2: 70-71
Translated by: Riyāḍ al-Kanadī