Penn’s music department is committed to world-class undergraduate and graduate education. Non-majors and musical beginners can chose from many courses, ranging from music theory and histories of opera, to world music, jazz, and the music of Africa. These introductory courses are numbered 000-099. More advanced undergraduate classes, intended for music majors and minors, are numbered 100-499. Offerings numbered 500-999 are considered graduate courses. See here for a general description of undergraduate courses and here for the graduate ones. At this link you find more info about courses related to performance.