أَوْ زِدْ عَلَيْهِ وَرَتِّلِ الْقُرْآنَ تَرْتِيلًا
[73:4]
Or add to it, and recite the Quran as it ought to be recited.
Or a little more; and recite the Qur'an in slow, measured rhythmic tones.
Or add (a little) thereto - and chant the Qur'an in measure,