You are correct about oft-quoted Luke 2:13, all major translations describing actions of the angels as "praising God and saying." The two verbs in Greek are ainountōn and legontōn, which may infer singing but are never translated that way. The phrase "to praise God joyfully with a loud voice" is a near parallel found in Luke 19:37. Again, singing isn't referenced but I can certainly 'hear' spontaneous song on the occasion.

Jim, I hope you'll forgive this off-topic digression, but Jamie's reference to the angels, the Magi and the Christmas story from Luke prompts this.

Scripture doesn't always employ the words we would prefer to be used, but they are clearly there. For example, in none of these passages are sun and moon, stars, planets, constellations or galaxies mentioned, but try to understand their meaning without them.

Psalms 19:1-4

The heavens declare the glory of God; the skies proclaim the work of his hands.
Day after day they pour forth speech; night after night they display knowledge.
There is no speech or language where their voice is not heard.
Their voice goes out into all the earth, their words to the ends of the world.

The same is true when the Apostle Paul references Psalms 19 in this passage -

Romans 10:17-18

Consequently, faith comes from hearing the message, and the message is heard through the word of Christ.
But I ask: Did they not hear? Of course they did: "Their voice has gone out into all the earth, their words to the ends of the world."

Let that sink in for a moment - "Did they not hear? Of course they did." A similar expression appears in this passage, begining with a series of questions about our response to God's creation -

Isaiah 40:21

Do you not know? Have you not heard? Has it not been told you from the beginning? Have you not understood since the earth was founded?

After having these passages explained, and being made to consider rather than skim the words, I don't walk outside anymore and look at the skies in a casual state of mind.