From Homestar Runner Wiki
The Hornblower or "Herald" is seen in The King of Town DVD as The King of Town's royal subject. When The King of Town feared for his sheep, it was this fair servant who summoned Homestar Runner and Pom Pom. In addition to his normal duties, he is a member of the K.O.T.H.S. Junior Varsity Marching Band and plays saxophone for All the King's Men!
He also appears in The House that Gave Sucky Treats as Thor the Caveman from the comic strip B.C.; watch for him as he occasionally wheels down the road on a unicycle during The King Of Town's segment. Additionally, he appears on the King of Town menu when you mouse over the "email" button.
The tune the Hornblower plays to summon Homestar Runner in the new version is "Homestar Run. Run." from the Theme Song Video. The instrument that the Hornblower plays is called the buisine. It was a long, conical brass instrument used by heralds in the Middle Ages.
The Hornblower is the only one of The King of Town's subjects that has yet to speak in a cartoon.