to yourselves - “to one another.” Hence soon arose the antiphonal or responsive chanting of which Pliny writes to Trajan: “They are wont on a fixed day to meet before daylight [to avoid persecution] and to recite a hymn among themselves by turns, to Christ, as if being God.” The Spirit gives true eloquence; wine, a spurious eloquence.
psalms - generally accompanied by an instrument.
hymns - in direct praise to God (compare Act 16:25; 1Co 14:26; Jam 5:13).
songs - the general term for lyric pieces; “spiritual” is added to mark their being here restricted to sacred subjects, though not merely to direct praises of God, but also containing exhortations, prophecies, etc. Contrast the drunken “songs,” Amo 8:10.
making melody - Greek, “playing and singing with an instrument.”
in your heart - not merely with the tongue; but the serious feeling of the heart accompanying the singing of the lips (compare 1Co 14:15; Psa 47:7). The contrast is between the heathen and the Christian practice, “Let your songs be not the drinking songs of heathen feasts, but psalms and hymns; and their accompaniment, not the music of the lyre, but the melody of the heart” [Conybeare and Howson].
to the Lord - See Pliny’s letter quoted above: “To Christ as God.”