Asaph was appointed as chief of the musicians as a young man by David and lived through the time of Solomon. He saw the height of the worship in the temple and the sad wickedness which started to take over even during Solomon's lifetime. He wrote Psalm 50 and 73-83 and is known as a "seer" and a warning type of prophet.
Three lessons to learn are 1) When the wicked prosper, get God's perspective, 2) When you are discouraged, remember God's power and 3) praise, listen and obey (open your mouth wide!).