Concerto No. 4 in E-flat Major, K. 495, is a standard professional work that is often required at orchestral auditions, university auditions, and competitions.  The piece was also originally written for natural horn, and the performer Joseph Leutgeb (1732-1811).  It too is a standard professional work that is within the capabilities of advanced high school students.  The difficulty in this piece lies in the nuance of performing in the classical style, while some additional technical challenges include cadential and internal lip trills, sixteenth-note runs, and the cadenza.