I called but got a tone: better boat out the borough posthaste
This line wraps up the previous references to “holy ark” (ie. Noah’s Ark) and “divine rage” (the Great Flood).
El called God and got a tone, which means God is either busy or ignoring him.
Another way to read this could be instead of getting “a tone”, El gets a one word response, “atone”, which means to make amends for your sins.
Either way, God isn’t going to help you here, so El takes matters into his own hands by taking a boat to escape the Flood.
Notice that alliteration is also used extensively in this line (ie. but, better, boat, borough).
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