We should not think that Israel’s hymn singing was anything like our four part harmony, or even singing in unison. Psalm 136 is an example of responsive singing, where one person or group says one line, and another repeats the refrain.
The Psalm reminds us of the greatness of God: He is supreme and without equal. He does unimaginable things – like create the heavens and the earth. He delivers His people from trial and does so with a mighty hand that makes his power obvious. He defeats the enemies of His people and blesses them abundantly. But not just His people; this God supplies the needs of all creation.
But above all these magnificent traits is one that outshines them all: His love does not end – a reminder that is repeated twenty-six times.