Is it permissible for the Imam leading the congregational prayer to excessively prolong the letters and lengthen the prayer?

The Qur'an and Sunnah have emphasized the importance of tartīl (reciting with proper articulation and melodious tone) and beautifying one's voice with it. Allah Almighty commanded: "And recite the Qur'an with [proper] recitation" (Quran 73:4). And the Prophet, peace and blessings be upon him, said: "Adorn the Qur'an with your voices." However, tartīl must not lead to altering the pronunciation or adding letters, as agreed upon by the jurists. This is further indicated by the Prophet's praise for the recitation of Salim, the freed slave of Abu Hudhayfah, and Abu Musa al-Ash'ari.