Sing a new song to the Lord ! Let the whole earth sing to the Lord ! Sing to the Lord; praise his name. Each day proclaim the good news that he saves. (Psalms 96:1, 2 NLT)
In the past I have wondered about this psalm, does it mean we can never repeat songs? You always need to sing new songs.
The other day the Spirit whispered to me that the new song is the song of salvation. In eternity past there has never been a time the God of all things came down from his thrown like he did for us, so even though it may be 2,000 years old, in terms of eternity this is still a very new song.