or add to it [at will]; and [during that time] recite the Qur'an calmly and distinctly, with thy mind attuned to its meaning.

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,

Or add to it, and recite the Qur'an in a leisurely manner.

Or add to it, and recite the Qur'an with measured recitation.