My father-in-law once told me that the saints of God will be the only ones singing in heaven. "What about the angels?" I asked. Without losing stride, he replied that nowhere does the Bible say that angels sing. They declare, they praise, they worship; he said, but they don't sing.
Now I've not checked all the references to determine whether or not my father-in-law's claim is true, but even so there is something important about his observation: the human voice is a unique instrument among God's creatures, and it is most uniquely played in the singing of songs.