LET THIS BE RECOGNIZED
Horns have a regular mode, where all you do is swing your horn around like some retard jacked up on cocaine, and performance mode.
In performance mode, your horn plays colored notes (which notes you have are determined by the horn and are easy to see when you craft it.) You can switch notes by hitting an attack button, which will cause your character to swing it before propping it in to a new position which inputs a different note.
The 3 different note inputs are
Side attacks (both are the same note)
and Down attack
For tables containing the melodies, see Hunting Horn Melodies .