AE 326 - singing & heavenly joy

AE 326
"To sing a song" signifies confession from joy of heart,
because joy of heart, when it is in fullness, expresses itself in song,
this it does because when the heart,
and in consequence the thought also,
is full of joy, it pours itself forth in singing,
the joy of the heart itself through the sound of the singing,
and the joy of the thought therefrom through the song.
The kind of joy of the thought is expressed by the words of the song,
which concur and agree with the matter that is in the thought from the heart;
the kind of joy of the heart is expressed by the harmony,
and the measure of this joy
is expressed by the exaltation of the sound and the words in it.
All these flow as if spontaneously from the joy itself,
and for the reason that the whole heaven is formed
according to the affections of good and truth,
the highest heaven according to the affections of good,
and the middle heaven according to the affections of truth;
it is therefore formed also for joys,
for every joy is from an affection, or from love;
from this it is that in all angelic discourse there is a kind of harmony.

[13] I will add to this an arcanum:
the angels who constitute in heaven the Lord's celestial kingdom,
when a person is reading the Word,
draw from his affection alone the internal sense of it,
which affection arises from the sound of the words in the original tongue;
but the angels who are in the Lord's spiritual kingdom
draw the internal sense from the truths that the words contain;
therefore the person who is in spiritual affection
has from the celestial kingdom joy of heart,
and from the spiritual kingdom confession from that joy.
The sounds of the musical instruments . . . elevate the affection,
and the truths give form to it.
That this is so is well known to those skilled in the art of music.
For this reason the Psalms of David are called "psalms,"
from psallere [to play]; they are also called "songs" from singing;
for they were played and sung
with the accompanying sounds of various instruments.