From the Publisher
The next step for students who have completed the advanced level method for their instrument. The full-page etudes in this series, key-centered and supported by scale and arpeggio exercises, take the student to that next level ofperformance wherein their accumulated skills allow them to play full-length performance pieces with a high level of musicianship and competence. As such, many states include these pieces in their all-state audition lists.
Difficulty level, roughly compared to ABRSM exam grades. 0 is beginner, 9 is advanced (beyond grade 8).