Sing unto the LORD with the harp; with the harp, and the voice of a psalm. With - the voice of a Psalm - I think זמרה zimrah, which we translate Psalm, means either a musical instrument, or a species of ode modulated by different voices.
Related Commentaries of Psalms 98:5
Psalms 98:5
5 Sing unto the LORD with the harp; with the harp, and the voice of a psalm.