Mythology & Beliefs: Polymnia (Polyhymnia) In Greek and Roman Mythology, Polymnia (Polyhymnia) was one of several Muses.
Polymnia in Greek and Roman Biography and Mythology
（Πολύμνια), or POLYHY'MNIA, a daughter of Zeus, and one of
the nine Muses. She presided over lyric poetry, and was
believed to have invented the lyre. (Hes. Th. 78; Schol. ad
Apollon. Rhod. 3.1.) By Oeagrus she became the mother of
Orpheus. (Schol. l.c. 1.23.) In works of art she was usually
represented in a pensive attitude. (Hirt, Mythol. Bilderb. p.
209; comp. MUSAE.) - A Dictionary of Greek and Roman biography
and mythology, William Smith, Ed.