The “throne” is the one of Revelation 4:1–11 upon which God himself was seated. Surrounding that throne were two semi-circles of divine attendants, an inner semi-circle of four living creatures (forming, as it were, an honour guard, see on Revelation 4:6) and an outer semi-circle of twenty-four elders (forming, as it were, a body of advisors). Inasmuch as these living creatures and elders are so intimately connected to God (= “the throne”), we are to understand that the song is sung specifically in the presence of God.
3 and they were singing a new song before the throne and before the four living creatures and before the elders. No one could learn that song except the 144,000 who had been redeemed from the earth.