"Before the throne, and before the four beasts, and the elders" is the same scene (FROM HEAVEN) that's detailed in Revelation 4 and 5. Furthermore, "no man could learn that song but the hundred and forty and four thousand, which were redeemed from the earth" indicates that the 144,000 are already in Heaven because that's where the singing is coming from and they're the only ones that can learn the song.