Many years ago I came across an amazing book by Bazak (I may be wrong but I think he was a Supreme Court judge and not Rav Amnon - but I might be mistaken) demonstrating the amazing symmetry in hallel, and that these series of Psalms were always meant to be prayed together.
I do not remember the exact numbers but in short there are 2 pizmonim exactly 20 words each (starting with yisrael betach.. and yomar na... respectively) and there are exactly 100 words in between and exactly 171 (?) words before and after them (leaving out the word haleluka)
And that the exact middle words is "ממות" in ki chilatzta...
And that phrase is the central theme.
I think about that last fact every time I say it.
Rabbi Benjamin Kramer
Director Educational Technology
Yeshivah of Flatbush H.S.
