GUIDO Music Notation is a formalism for adequately representing score-level music that has been developed by Holger H. Hoos, Keith A. Hamel, Kai Renz and Jürgen Kilian. Since its introduction in 1997, it has stirred considerable interest in the computer music community and among notation software developers. The talk will give an introduction on Basic and Advanced GUIDO features and their use for representing Conventional Music Notation (CMN). We will demonstrate how exact score formating can be realised with Advanced GUIDO. Furthermore, the GUIDO NoteServer and its different modes of access (including JAVA, CGI) will be presented. A short description of the main design principles of our own GUIDO applications will also be given.