I have heard at least four nuschaos (liturgies) for the very end of Yishtabach between habocheir b'shirei zimrah (who chooses musical songs of praise) and chai/chei* haolamim (life/life-giver of the world):†
- הַבּוֹחֵר בְּשִׁירֵי זִמְרָה חֵי הָעוֹלָמִים ( – nothing – )
- הַבּוחֵר בְּשִׁירֵי זִמְרָה מֶלֶךְ אֵל חֵי הָעוֹלָמִים (King, God)
- הַבּוחֵר בְּשִׁירֵי זִמְרָה מֶלֶךְ יָחִיד חֵי הָעוֹלָמִים (unique King)
- הַבּוחֵר בְּשִׁירֵי זִמְרָה מֶלֶךְ יָחִיד אֵל חֵי הָעוֹלָמִים (unique King, God)
What is the reason (and source) for each version?
* The nikkud of ches varies, but is not the subject of this question. The examples are vowelized solely for readability.
† Punctuation has been removed from the examples to further lessen variation that is not the subject of this question.
1. E.g. Teimani Baladi (Yemen).
2. E.g. Ashkenaz (German), Adot ha-Mizrach (Sephardic), Munkacz (Chassidic).
3. E.g. Chabad (Lubavitch), Lev Tahor (Chassidic)
4. E.g. Common Sfard (Chassidic).