This paper presents a technique for enhancing music information by annotation, and we apply the technique of annotated music to a collaborative music creation system on the Web, Music Resonator (MR). In MR, a user retrieves music fragments from Pool, processes them on Operation Diagram Editor and shares new music fragments with others, just as people readily exchange emails through mobile phones. Since a music fragment in MR is annotated with analysis results based on music theory, a user can perform complicated, skillbased tasks easily and properly. The result of a preliminary evaluation using the current implementation supports the significance of annotated music.