iClefs is a replacement for your music stand, allowing you to carry thousands of sheets of music in your iPad, annotate them, and display them during live performances, tapping each page to turn it (or to jump to another page).
iClefs comes with over 200 works of classical music ... already annotated with "jumps" (repeat sign, DS, DC, Coda, etc.) where a tap will take you to the target.
Using iClefs (via iTunes), you can import your own music or share your own annotations with other iClefs users.
Most iClefs screens have context-sensitive help ... just tap the "i" on the upper right of the navigation bar at the top for help.