A Maskil: This may be a literary or musical term.
Heman the Ezrahite: Heman might have been:
a wise person from the time of King Solomon (1 Kings 4:31),
a descendant of Judah (1 Chronicles 2:6), or
a member of the Levite family responsible for singing at the temple (1 Chronicles 15:17; 2 Chronicles 5:12).