Ephesians 5:19

λαλοῦντες ἐαυτοῖς. Cf. Ephesians 4:32. In the parallel Colossians 3:16 we find διδάσκοντες καὶ νουθετοῦντες ἐαυτοὺς ψαλμοῖς κ.τ.λ. It seems natural therefore to take λαλοῦντες (as e.g. in 1 Peter 4:11) of speaking in the Christian assembly. The thought of the social gatherings of the heathen suggested by μὴ μεθύσκεσθε οἴνῳ would call up at once the thoughts of Christian gatherings esp. for Agapè or Communion and the music and song by which they were accompanied.

ψαλμοῖς κ.τ.λ. Cf. Lightfoot on Colossians 3:16. The ref. here is prepared for by the quotation in Ephesians 5:14.

ᾄδοντες καὶ ψάλλοντες τῇ καρδίᾳ ὑμῶν τῷ κυρίῳ. The heart is lifted up to the Lord while the mouth is giving expression to its joy in the congregation. In music in the congregation, ritual expression is in danger of outrunning the inward devotion. In the matter of public confession of faith in the sight of an opposing world, the danger is the other way, and the order of reference to heart and mouth is reversed in Romans 10:10.