Rashi comments in Parshat Emor 23:24 on the pasuk “zichron teruah,” that we are obligated to recite the berachos of zichronot and shofarot on Rosh Hashana. This would presumably be a biblical commandment, beyond the obligation to blow the shofar,that there is an additional mitzvah to recite the berachot of zichronot and shofarot. (The source for the obligation to read malchiyos is based on a pasuk in Parshat Behaalotecha 10:10.) The Ramban takes issue with Rashi in three different places – in his commentary on the Torah, his additions to Sefer Hamitzvos and in his derasha to Rosh Hashana – arguing that the obligation is only rabbinic in nature, and the sources are only asmachtot. The Ramban’s primary proof against Rashi is the Gemara in Rosh Hashana , which says that if a person has to choose between hearing the shofar and a chazzan who will recite the berachot of malchiyot, zichronot and shofarot, he should go to hear the shofar because it is deoraita, as opposed to the derabbanan berachot. This seems to be a direct contradiction to Rashi who holds the berachot are deoraita.
Several Acharonim offer approaches to defend Rashi. Rav Shlomo Zalman Auerbach, based on the language of Rabbenu Chananel, argues that to fulfill the chiyuv min hatorah all one must say is a brief statement including malchiyot, zichronot and shofarot. The Gemara, however, is discussing the entire nusach which we say, which is not biblically required. It therefore concludes that one should say a short statement including all three and hear the shofar. Alternatively, the Yom Teruah says that when the gemara says derabbanan it really means a biblical obligation that is learned from Torah Shebe’al Peh, which Rambam often refers to as divrei sofrim,. However, this approach is difficult because the gemara clearly says derabanan, not divrei sofrim. The Yom Teruah gives a second approach based on the Gemara on daf 29, where the gemara uses zichron teruah to refer to Rosh Hashana that falls on Shabbos, arguing that only when there is no tekiat shofar will there be a Torah obligation to recite malchiyt, zichronot and shofarot. Both Rav Yitzchak Zev Soloveitchik and Yosef Dov Soloveitchik are quoted as saying that the obligation to recite the berachot is deoraita when it accompanies the tekiot, while berachot said on their own without shofar are only Rabbinic. Ramban’s proof case, then, is a case where the berachot are not said in conjunction with shofar and thus are only rabbinic.
The idea expressed by Beis Brisk can be taken one step further. There is a machloket between the Baal Hamaor and the Ramban regarding the nature of the second set of tekiot we say al seder haberachot. The Baal Hamaor holds that those are the ikar tekios, going so far as to say that the original beracha recited on the shofar; was not “asher kideshanu lishmoa kol shofar” but the malchiyot, zichronot and shofarot. Assuming these berachot are birakot hamitzvah that relate to the mitzvah of shofar, this Rashi can be better understood in light of a Rashi in Parshat Ki Tavo. On the pasuk “velo shachachti” in the context of in viduei maser, Rashi explains that one says he has not forgotten to make a beracha on the maser, implying that birkas hamitzvah on ma’aser sheni is deoraisa, which is difficult in light of the Gemara in Berachos that says birkos hamitzvah are rabbinic. It is possible to explain that, though not all mitzvos warrant a beracha min hatorah, it is possible that a beracha is needed in the case of ma’aser sheni to differentiate this eating from a mundane “snack” of fruits. Similarly, tekiat shofar is not only a maaseh mitzvah like lulav, sukkah and matzah but is a zichron teruah, a vehicle of Tefillah that is recalls our zichronot lifnei vilifnim. The gemara in Rosh HaShanah says the rule of ein kategor na’aseh saneigor applies to shofar because it goes lifnai vilifnim like bigdei kehuna of the Kohen Gadol. This statement, as well as the Gemara’s comparison bewteen one’s posture in tefillah and the shape of the shofar, shows that there is an aspect of Tefillah in shofar. The beracha integrates with the mitzvah because by describing the themes of the shofar and the day of Rosh Hashanah we transform the shofar from merely kol tekiatenu to kol tefilateinu.