St. Ephrem, an influential saint from the 4th century, is known as the "Harp of the Holy Spirit."
Why is that?
St. Ephrem is called the "Harp of the Holy Spirit" primarily because of the number of hymns and poems that he wrote.
Even his homilies were written in verse, according to the Catholic Encyclopedia.
As a result, "[i]n the East the Lessons for the ecclesiastical services were often taken from the homilies of Ephraem."
Even today St. Ephrem's hymns and homilies are used extensively in various Eastern Christian liturgies.
St. Ephrem was clearly inspired by the Holy Spirit and let that inspiration form everything that he wrote.