Harp music is identical to piano music. I took piano lessons for four years before I began playing the harp. This provided me with all the music theory I needed. One major difference between harp and piano is that you never use your pinkie finger to play any notes on the harp. This makes all the fingering, quite different from the piano. Harpists often mark their music with the number of the finger above the note and other signs to help themselves remember the fingering. I have thoroughly enjoyed playing many of my piano pieces on the harp.
Don't worry I haven't forgotten about jazz harpist, and harp therapy is a whole other category. I'll post some more about them soon. As for now, thanks for reading! Please leave questions and comments!