See Definition for 5215
See Definition for 5568
See Definition for 5603
5603 is the generic term; 5568 and 5215 are specific, the former designating a song which took its general character from the OT Psalms, although not restricted to them, the later a song of praise. While the leading idea of 5568 is a musical accompaniment, and that of 5215 praise to God, 5603 is the general word for a song, whether accompanied or not, whether of praise or on any other subject. Thus it is quite possible for the same song to be at once described by all three of these words.