I’m not sure about the ‘chain’ wordwind, but I think Homer may be describing the “high thin cries” coming from the bat that drops from the chain, rather than the remaining bats. The passage is rather ambiguous on that point: in one part of the passage, Homer’s words of “as bats cry in the depths of a dark haunted cavern, shrilling, flittering, wild when one drops from the chain—" suggests that the remaining bats in the ‘chain’ cry as one bat drops. But then he follows that up with, “while the rest cling tight”, which seems to suggest that it is the one bat crying, leaving ‘the rest [to] cling tight’.

Since bats use a type of sonar to navigate by making a high-pitched noise (a ‘high thin’ cry as Homer calls it), which bounces off of the surrounding objects and returns to the bat, it would make more sense to me for the one bat leaving the ‘chain’ to make the noise for navigation purposes, than for the remaining bats to make the noise, since they have no need to navigate.