Jamieson, Fausset and Brown on 1 Corinthians 14:26

26. How is it then?--rather, "What then is the true rule to be observed as to the use of gifts?" Compare 1Co 14:15, where the same Greek occurs.

a psalm--extemporary, inspired by the Spirit, as that of Mary, Zechariah, Simeon, and Anna (Lu 1:46-55, 67-79; 2:34-38).

a doctrine--to impart and set forth to the congregation.

a tongue ... a revelation--The oldest manuscripts transpose the order: "revelation ... tongue"; "interpretation" properly following "tongue" (1Co 14:13).

Let all things be done unto edifying--The general rule under which this particular case fails; an answer to the question at the beginning of this verse. Each is bound to obey the ordinances of his church not adverse to Scripture. See Article XXXIV, Church of England Prayer Book.