Some translations set each line of poetry farher to the right than the rest of the text to make it easier to read. The ULB does this with the poetry in 15:3-4.
##### "The most holy place, in which was the tent of witness, was open in heaven" #####
This statement has led some scholars to believe that the Jewish temple reflected a scene in heaven. (See: [[rc://en/tw/dict/bible/kt/heaven]] and [[rc://en/ta/man/translate/writing-apocalypticwriting]])
##### Songs #####
Heaven is often described as a place where people sing. These are songs of worship to God. This illustrates that heaven is a place where God is continually worshiped.