The Petrucci Music Library is an essential database for musicians, music librarians and teachers, as well as lovers of classical music. The online collection shares public domain music via a searchable interface. On the main page, visitors may search for works by composer (or composer's nationality), genre, time period, or melody. Searching by melody is particularly interesting, as it launches an interactive keyboard on which users may play (or, for those of us less musically inclined, attempt to play) a familiar melody in order to search the database for it. Some searches will yield YouTube clips of the music. The website also provides scans of sheet music from many composers, genres and world locations. [AHT]