Jamieson, Fausset and Brown on Revelation 14:3

3. sung--Greek, "sing."

as it were--So A, C, and Vulgate read. It is "as it were" a new song; for it is, in truth, as old as God's eternal purpose. But B, Syriac, Coptic, Origen, and Andreas omit these words.

new song--(Re 5:9, 10). The song is that of victory after conflict with the dragon, beast, and false prophet: never sung before, for such a conflict had never been fought before; therefore new: till now the kingdom of Christ on earth had been usurped; they sing the new song in anticipation of His blood-bought kingdom with His saints.

four beasts--rather, as Greek, "four living creatures." The harpers and singers evidently include the 144,000: so the parallel proves (Re 15:2, 3), where the same act is attributed to the general company of the saints, the harvest (Re 14:15) from all nations. Not as Alford, "the harpers and song are in heaven, but the 144,000 are on earth."

redeemed--literally, "purchased." Not even the angels can learn that song, for they know not experimentally what it is to have "come out of the great tribulation, and washed their robes white in the blood of the Lamb" (Re 7:14).