Revelation 9:13–15 relate connected actions, as is clear from the sequence of verbs: the trumpet is blown, a voice speaks, four bound angels are released. Revelation 9:16–19 describe in detail what appeared in consequence of the initial series of actions. Revelation 9:20–21 inform the reader of humanity’s response to the plagues that follow the sixth trumpet.
13 Then the sixth angel blew his trumpet, and I heard a voice from the four horns of the golden altar before God,