ONLY ONCE A YEAR DO THEY SAY IT

ONLY ONCE A YEAR DO THEY SAY IT אחינו בני עדות המזרח (Sefardim)  don't say יוצרות not on Yomim-Noraim, Yamim-Tovim or on The Arba Parshios. The only exception is on Shabbos  Parshas זכור.  These יוצרות are called "מי כמוך". It starts with the Piyut of R.Yehuda Halevi "אדון חסדיך" The ספר סדר הדורות writes, When R. Yehudah Halevi wrote the Piyut "אדון חסדיך" he took a break at the Stanza of the letter ר (Reish). The Ibn Ezra passed by and continued on his own the Stanza on the letter ר. R.Y.Halevi was so impressed with the stanza that he left it in the Piyut and continued on. He also took him as a son in law as a result of this. Hence, the two stanzas for the letter  ר .