Before we (Ashkenazim) recite the Hallel we make a blessing which concludes "likro et hahallel" (to read the Hallel). Is there any law which is derived from this? Does it invalidate reciting/saying the Hallel by heart?
The Sephardi custom is to say "ligmor et hahallel" (at least when reciting the whole hallel -- I haven't seen any other discussion) but "completing" the Hallel is essential.
[Hacham Ovadia] notes that the Maharam of Rotenberg (Rabbi Meir Ben Baruch, Germany, 1215-1293) held that it is actually preferable to recite the text of "Likro Et Ha'hallel." If one recites "Ligmor Et Ha'hallel," which means "to complete the Hallel," and he mistakenly omits a word from the Hallel recitation, then the Beracha that he recited would thus be rendered a "Beracha Le'vatala" (Beracha recited in vain). The Maharam therefore preferred reciting "Likro Et Ha'hallel" so that the Beracha would remain valid even in the event that somebody mistakenly omits a word.
Is the Ashkenazic choice of verb similarly essential?