The name 'Heman' is a Jewish name, meaning 'Faithfull'. You will find it approximately 10 times in the bible (eg. see: 
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The Psalm written by Heman seems to have been written in a state of despair. According to Martin Marty, a professor of church history at the University of Chicago, Psalm 88 is “a wintry landscape of unrelieved bleakness.”
Psalm 88 ends by saying:
You have taken my companions and loved ones from me; the darkness is my closest friend. (Psalm 88:18, NIV).
Indeed, in Hebrew, the last word of the Psalm 88 is "darkness" The only other Psalm in the Bible that similarly ends without any hope is Psalm 39.