"LET" AND "BE FILLED"
One very significant aspect of Kingdom singing is that it's a way of exhorting, comforting or building up other Believers and our own selves while doing it.
Singing the word of Christ in thanksgiving, praise, worship or prayer has power.
In Colossians and Ephesians, the Lord makes two exhortations about singing. And it also goes to show that our Father wants His Children to be singers.
However, before each exhortation the Spirit emphasises some spiritual character aspects that Believers should have when singing.
Added to these spiritual character aspects, each exhortation (in italics) begins with a requirement: "Let the word of Christ dwell in you ..." and "Be filled with the Spirit ...".
In Colossians 3'12-16:
"Therefore, as the elect of God, holy and beloved, put on tender mercies, kindness, humility, meekness, longsuffering;
bearing with one another, and forgiving one another, if anyone has a complaint against another; even as Christ forgave you, so you also must do.
But above all these things put on love, which is the bond of perfection.
And let the peace of God rule in your hearts, to which also you were called in one body; and be thankful.
Let the word of Christ dwell in you richly in all wisdom,
teaching and admonishing one another
in psalms and hymns and spiritual songs".
In Ephesians 5'14-19:
"'Awake, you who sleep, arise from the dead, and Christ will give you light'.
See then that you walk circumspectly, not as fools but as wise,
redeeming the time, because the days are evil.
Therefore do not be unwise, but understand what the will of the Lord is.
And do not be drunk with wine, in which is dissipation; but
be filled with the Spirit,
speaking to one another
in psalms and hymns and spiritual songs,
singing and making melody in your heart to the Lord".
The flowing of the ministries of psalms, hymns and spiritual songs blesses everyone in many ways (together with the manifestation of the Spirit in the ministering of God's gifts, of course).
These two exhortations involve Believers with the Holy Spirit and the word of Christ for "teaching and admonishing one another and "speaking to one another".
"Singing and making melody in your heart to the Lord" is all part of the way God's People are built up as Jude 1'20 says:
"But you, beloved, building yourselves up on your most holy faith".