Q. See question above. Does the taking off the Tefilin on Rosh Chodesh have anything to do with what kind of nusach one recites during the Kedusha?

The Rema adds that this is only necessary in places where the Kedusha of Musaf begins with the phrase, “Keser yitnu lecha” (A crown will be given to You [Hakodosh Boruch Hu]). (This is the text of Kedusha known as Nusach Sefarad.

The Mishnah Berurah (25:61) explains that it is inappropriate to wear tefillin, which is our crown, while referring to the crown of Hashem.

Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a.