Sing unto the Lord with the harp,.... Playing upon that at the same time: here and in the following verse is an allusion to Old Testament worship, and the manner of performing that; not that this should be done in New Testament times, only New Testament worship is expressed in Old Testament language, which is no unusual thing; hence in Gospel times, and Gospel churches, the saints, especially when singing the new song of redeeming grace, are said to have harps in their hands, expressive only of their spiritual melody in their hearts, Rev 5:8, with the harp, and the voice of the psalm; with the harp alone first, as Aben Ezra and Kimchi interpret it, and then with the harp, and together with the words of a psalm, sung in a psalm tune. Gospel churches are to sing psalms, hymns, and spiritual songs, Eph 5:19.