The various texts of the prayer found among the various communities of the Jewish nation all have strong and holy roots. Therefore, one should not deviate from the prayer text that one’s forefathers were accustomed to. Hence, a Sephardic individual should not adopt the prayer text of Ashkenazi communities (or the text called “Sefard” which is the prayer text followed by Hassidic Jews); rather, one should follow the prayer text of the Middle Eastern communities. Similarly, an Ashkenazi individual should not adopt the Sephardic prayer text.
Indeed, the Magen Avraham writes that the Ari z”l is quoted as saying that there are twelve tribes in Heaven and each one of these tribes has a gate and a custom. It is for this reason that one should not deviate from the custom of one’s fathers with regards to the texts of the prayer. Several great Poskim write likewise.
Nevertheless, Maran Ha’Chida writes that the Ari z”l himself who was Ashkenazi, related to the great Rabbeinu Shlomo Luria (Maharshal), would pray according to the Sephardic prayer text all year round besides for the High Holidays, as he writes in his Sha’ar Ha’Kavanot. Maran Ha’Chida adds that the Sephardic prayer text ascends through all twelve gates in Heaven. Based on this, it would seem that an Ashkenazi individual may change his custom and begin praying in accordance with the Sephardic prayer text. This was indeed the custom of Hagaon Harav Natan Adler zt”l, rebbi of Hagaon Harav Moshe Sofer (the “Chatam Sofer”), and Hagaon Harav Pinchas Ha’Levi Ish Horowitz zt”l, author of the Sefer “Hafla’a” on Masechet Ketubot. (Not only that, but Hagaon Harav Natan Adler zt”l would even recite the prayer with the Sephardic pronunciation of the letters and vowel sounds as he believed that this was indeed the correct pronunciation. Indeed, he hired Hagaon Harav Yitzchak Moda’i z”l from Turkey to teach him the Sephardic pronunciation of the letters and vowel sounds and would not allow anyone to serve as Chazzan in his synagogue; rather, he alone would serve as Chazzan while reciting the prayers in a Sephardic pronunciation. Similarly, Hagaon Harav Yaakov David Volovsky zt”l, author of the Responsa Ridbaz, writes in one of his responses to Hagaon Chacham Yosef Mordechai Yedid Ha’Levi of Aleppo, Syria: “Indeed, the pronunciation of Lashon Ha’Kodesh in your communities is much more correct, for due to the lengthy exile, the Ashkenazim have become extremely scattered and distanced in their mode of dress, writing, and language, this one to the east and that one to the west; even their mundane language has become mixed up.”) Nevertheless, the Chatam Sofer writes that after the passing of the saintly author of the Sefer Hafla’a, his son, the saintly author of the Machaneh Levi, closed down his synagogue. It seems that in his opinion, an Ashkenazi individual should not change to pray in accordance with the Sephardic prayer text. This matter is obviously subject to a disagreement among the Poskim. In any case, a Sephardic individual should certainly not change to pray in accordance with the Ashkenazi prayer text, neither with regards to the actual prayer text nor with regards to the pronunciation of the words.
Similarly, it is not permissible to pray according to the “Standard Text” common in several places, among them in the Israel Defense Forces, as this text is predominantly Ashkenazi with some Sephardic texts mixed into it; thus, one should not follow this version at all.
Hagaon Harav Avraham Yitzchak Ha’Kohen Kook zt”l writes lengthily in his approbation to the book authored by Hagaon Harav Ben-Zion Meir Hai Uziel zt”l that an Ashkenazi individual should not change to Sephardic pronunciation, for this constitutes the prohibition of “Do not forsake the laws of your mother,” among other reasons he lists. Clearly though, others disagree with his opinion and maintain that the Sephardic pronunciation is more correct and one may indeed change to it. Unfortunately, nowadays, many people have changed their pronunciation to a new kind of pronunciation of the letters which is similar to the Sephardic version, but in truth is not Sephardic at all, for they pronounce the letter “Het” like the letter “Khaf,” the letter “Kuf” like the letter “Kaf,” and other such mistakes. Such a pronunciation is completely mistaken and incorrect according to all opinions. Thus, it is incumbent upon every individual to try and perfect his pronunciation as much as possible so that he may merit praying in a language that is more articulate and accepted before Hashem. If one cannot change one’s pronunciation, one may continue pronouncing the words in the way one is accustomed to, for according to the letter of the law, one may even pray in a foreign language altogether (referring to any language besides for Lashon Ha’Kodesh); certainly, the erroneous form of Lashon HaKodesh spoken today is better than a completely foreign language.