I realized two things about the instrumental section (which starts at ~1:50 in this performance but at ~1:40 in the studio recording). Years ago, I figured out two of the vocal parts. They're something like:
The higher part generally descends, and the lower part ascends. This simultaneous up-and-down illustrates the confusion that's mentioned in the lyrics that come before and after this section. The preceding line is "But by now that answer just ain't true," and the next lyrics are "My world is spinnin' around / Ev'rything is lost that I've found." The vocal parts' going two different directions provides a sense of this disorientation.
Alternatively, this simultaneous up-and-down gives a musical picture of that see-saw. It's like each vocal part is an end; as one goes up, the other comes down.
