I guess it's possibly just a mistake that slipped into Ashkenaz siddurim - it wouldn't be the first. But my understanding of how eager many 17th Century Ashkenaz rabbis were to adopt ideas and practices of Tzfas kabbala makes me think that it was more likely intentional.
You make a good point about distinguishing between innovation and popularization. And I think it would touch on something I've thought about a bit: have changes in Jewish practice more often been the result of popular, bottom-up pressures, or rabbinic, top-down influence. My uneducated guess tends to lean to the bottom-up model.
I guess it's possibly just a mistake that slipped into Ashkenaz siddurim - it wouldn't be the first. But my understanding of how eager many 17th Century Ashkenaz rabbis were to adopt ideas and practices of Tzfas kabbala makes me think that it was more likely intentional.
You make a good point about distinguishing between innovation and popularization. And I think it would touch on something I've thought about a bit: have changes in Jewish practice more often been the result of popular, bottom-up pressures, or rabbinic, top-down influence. My uneducated guess tends to lean to the bottom-up model.
In אזור אליהו it says it's indeed a mistake, and even according to the kabbalists it wouldn't belong before pesukei dezimra for nusach ashkenaz.
I should add this link to an excellent discussion of the Mizmor Shir issue: https://www.hidabroot.org/question/41631