They sing: as noticed in 13.12, Revised Standard Version reproduces the present tense of the Greek verb; for purpose of narrative most translators will prefer to continue to use the past tense, as Good News Translation and other modern translations do. Who is the subject? As it stands in Greek, and as translated by Revised Standard Version and others, it can be the harpists of the previous verse. But this seems quite unlikely. Most translations reproduce the Greek form quite mechanically, but this should not be done unless the translator concludes that the harpists are the ones doing the singing. A number of commentators believe the singers are the countless angels surrounding God’s throne (see 5.11-12; 7.11-12). Others, however, believe that the 144,000 are the singers, as made explicit by Good News Translation, and Bible en français courant “these thousands of people were in front of the throne”; also similar is Nova Tradução na Linguagem de Hoje. It is recommended that the singers be identified as the 144,000 redeemed. So Good News Bible‘s rendering provides a good translation model.
A new song: as in 5.9.
Before the throne … the four living creatures and … the elders: see the description of the heavenly throne room in chapter 4.
No one could learn that song: to ask who would be teaching that song to the 144,000 goes beyond the writer’s intention in giving this information. This is a way of saying that only these 144,000 could sing this song—it could be sung by no one else.
Who had been redeemed from the earth: here the earth represents the earth’s inhabitants, the human race (see “redeemed from mankind” in verse 4). Of all people on earth these are the ones who had been redeemed. For redeemed see “ransom” in 5.9. If it is necessary to use the active voice of the verb, the translation can say “whom God has redeemed,” “whom God has saved.” This sentence may also be expressed as “They are the people whom God has saved.”
Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .