Rabbi, Thank you so much for your detailed response. Where online can I purchase the seforim that you mentioned? I’ll list a few of the criticisms of the Sepharad Siddur that I have come across. 1. The Siddur is imprecise, as it added words in an unsophisticated way to the Ashkenazi Siddur. 2. There are many double formulations that do not always go well together, such as the ending to the "Shomea Tefilah" blessing of the Amidah prayer. 3. The changes to the Siddur violated Halacha. 4. The grammar in the Nusach Sepharad Siddurim is often inaccurate. Can you please respond to these criticisms (in short of course, I understand a full explanation would be too long)? These criticisms concerned me, since I have used Nusach Sepharad since I got involved in Judaism roughly nine years ago. Also, how do we know what Nusach the AriZal referred to? He didn’t write much. I understand that Rabbi Chaim Vital transcribed much of the AriZal’s teachings. Is this true? Did he record the Siddur? Where does the Koren Nusach Sepharad Siddur come from if there are so many different versions to choose from? Thanks again for your response.

Shalom, I am glad that my previous answer was of some help to you. (Unfortunately I am unable to direct you to where you can purchase the books). In connection with your questions - Your questions can be divided into three major issues. 1) Grammatical questions about the Sefard siddur, 2) Halachic questions about the process of changing from the Ashkanazic siddur in the first place, and 3) Historical questions about the different versions of the Sefard siddur that we find today. As to the grammatical questions – it is true that there are many issues with the grammar of the Sefard siddur, and some of it has to do with the inaccurate printings that existed. The Sefard siddur of Chabad (Tihillat Hashem) is famed for having been edited with great accuracy by the first Lububitcher Rebbe, and all the grammatical issues that arise in it have deep explanations. The Koren siddur you mention has extensive notes in the back that explain many of the textual changes they made. But, in general, you should know that all versions of the siddur (including Ashkanaz) have issues. The Mishna Brurah quotes in various places different versions of the prayers, and discusses which versions are more acceptable than others. I would summarize by saying that the grammatical questions are either a) the result of printing mistakes, b) have grammatical explanations, or c) are based on kabbalistic teachings. In any case, as far as I know, none of them invalidate the prayers, and are probably a small price to pay in order to continue your family custom, and be part of your community prayers. The halachic question as to how the original changes were made to the siddur, you should see the response of Rav Feinstein zt"l (Igrot Moshe, Orach Haim 2, 24) where he addresses this question. Even though he casts doubts on the acceptability of those who first made the changes, he concludes that we do not cast doubt on those who made the original changes, as they must have had on whom to rely. There has been much written about this issue, but the bottom line is that today nusach Sefard is an acceptable version of the siddur. As to the historical questions, I must admit that it is not my field of expertise. May I suggest some on-line research? May you be blessed to have all your prayers heard on high, together with those of all Israel.