Querying the Hivemind: Songs about Songs

[Proginoskes]

From Personnent Hodie:

Omnes clericuli
Pariter pueri,
Cantent ut angeli:
Adventisti mundo,
Laudes tibi fundo.

Translated (via Google translate and reasoned guessing):

May all the clergy
And likewise the boys
Sing as the angels:
Of Advent, to the world,
Praise from our deepest souls.

First verse and chorus of Come, sing a song with me:

Come, sing a song with me,
Come, sing a song with me,
Come, sing a song with me,
That I might know your mind;
And I'll bring you hope, when hope is hard to find,
And I'll bring a song of love, and a rose in the wintertime.

First few lines of My Spirit Sang All Day (might not count, since it's about singing rather than song, and the rest is a fairly generic love song, but it's close):

My spirit sang all day,
Oh, my joy!
Nothing my tongue could say,
Only my joy!

Similarly, the first four lines of What Sweeter Music:

What sweeter music can we bring
Than a carol, for to sing
The birth of this our heavenly King?
Awake the voice! Awake the string!

Hurrah for doxologies!

In greening lands begins the song
which deep in human hearts is strong.
In cheerful strains your voices raise,
to fill the whole spring world with praise!

Hurrah for rounds!

Sing and rejoice,
Sing and rejoice,
Let all things living now
Sing and rejoice.