The snapshot link provided here for asdf-install is insufficient: you will need to perform additional steps documented in the INSTALL file before running gsharp for the first time, to make the font files needed by the application.
Gsharp is a graphical, interactive score editing application for standard Music notation. It can be customized by dynamically loading new Lisp code. The Gsharp user interface is based on CLIM. Source code, documentation and sample output are available at the project site.