The song beginning אנעים זמירות (also named Shir HaKavod), which is popularly sung in shuls on Shabbos and/or Yom Tov and/or Yamim Noraim, basically follows a letter-scheme, with one verse for each letter.
However, when it comes to the letter Reish (ר), there are two verses instead of one:
רוֹצֶה בְּעַמּוֹ עֲנָוִים יְפָאֵר/ יוֹשֵׁב תְּהִלּוֹת בָּם לְהִתְפָּאֵר
רֹאשׁ דְּבָרְךָ אֱמֶת קוֹרֵא מֵרֹאשׁ/ דּוֹר וָדוֹר עַם דּוֹרֶשְׁיךָ דְּרוֹשׁ
Why is this? Do we know if one of these two lines were always there (as the second of these two lines has a bit of an awkward rhyming scheme due to the enjambment)