There is an analogy of form between the sound of people singing together and the unity to which the church aspires, and for this reason music is a particularly apt vehicle for worship. In Ephesians 5, it is in connection with the command to be filled with the Holy Spirit that Paul urges his readers to sing. Music offers a sounding image of the kind of diversified unity brought about by the Holy Spirit—“simultaneous voices which are nevertheless also one voice.” “There are many parts, but one body,” is how Paul expresses the same ideal in 1 Corinthians (12:20). It is by the Spirit that Christians are baptized into one Body (1 Cor. 12:13); but it is also the Spirit who gives diverse gifts (1 Cor. 12:7‐11)—who gives to each part of the body its special function, to each voice its distinct part in the great chorus.
—Stephen R. Guthrie, “Singing, in the Body and in the Spirit,” Journal of the Evangelical Theological Society 46/4 (December 2003), 644
Finally, it is at the climax of these warnings and exhortations [in Ephesians 4 and 5] that Paul writes: “Be filled with the
Spirit. Speak to one another with psalms, hymns and spiritual songs. Sing and make music in your heart to the Lord” (5:18‐19). In other words, to a Christian community surrounded by
ignorance and immorality; to a people who themselves were prone to the blindness and
indulgence of their former way of life; at the conclusion of a passage warning against
irrationality and sins of the flesh—Paul urges singing and music making. . . . Paul shares the
same broad concerns as Augustine and Calvin, but the recommendation emerging from those
concerns is entirely different. To put it very crudely, Augustine says: “Irrationality is bad.
Sensuality is bad. Therefore, be careful about music.” Paul on the other hand says, “Foolishness
is bad. Sensuality is bad. Therefore, you had better sing.”]
–Stephen R. Guthrie, “Singing, in the Body and in the Spirit,” Journal of the Evangelical Theological Society 46/4 (December 2003), 638.