From Neil W. Levin's Introduction to Volume 14:

In the rendition of un’tanne tokef in Volume 14 that is attributed to Moshe Koussevitzky—originally an improvisation that he replicated in more or less the same way each year on Rosh Hashana and Yom Kippur at his synagogue in Brooklyn, New York—the repeated words and phrases make structural sense; and they reflect the imagery of the piyyut by intuiting and interpreting multiple layers of meaning. Whether he would have felt it necessary to reduce the rendition at his prewar khor shul pulpit in Warsaw we cannot know (this improvisation stems from his American years), although its dignity and appropriateness to text as well as occasion are not inconsistent with khor shul standards or those of the modern brand of orthodoxy promoted by those synagogues.