The Hymmnote II is a bonus booklet that was bundled with the preorders for the Ar tonelico II: Melody of Metafalica Original Soundtrack in Japan, and it contains most of the sheet music to both the opening and ending themes of the game: Singing Hill - Harmonics FRELIA - and EXEC_with.METHOD_METAFALICA/., and it also reveals a couple of lines in the latter that weren't published in the lyrics booklets of any of the albums.
Currently, it's a relatively rare item, although much less than its predecessor, the Hymmnote, which makes it comparatively cheaper and easier than acquire than the above mentioned booklet.