'New Song' in the Bible

And they are singing a new song--'Thou art worthy to take the book and break its seals, for thou wast sacrificed, and with thy blood thou didst buy for God men of every tribe, and language, and people, and nation,

They are singing what seems to be a new song, before the throne, and before the four Creatures and the Councillors; and no one was able to learn that song except the hundred and forty-four thousand who had been redeemed from earth.