Guido

GUIDO is designed to represent music in a logical format (with the ability to render to sheet music), whereas Lilypond is more narrowly focused on typesetting sheet music.

GUIDO is not primarily focused on conventional music notation, but has been invented as an open format, capable of storing musical, structural, and notational information.

GUIDO Music Notation is designed as a flexible and easily extensible open standard. In particular, its syntax does not restrict the features it can represent. Thus, GUIDO can be easily adapted and customized to cover specialized musical concepts as might be required in the context of research projects in computational musicology. More importantly, GUIDO is designed in a way that when using such custom extensions, the resulting GUIDO data can still be processed by other applications that support GUIDO but are not aware of the custom extensions, which are gracefully ignored. This design also greatly facilitates the incremental implementation of GUIDO support in music software, which can speed up the software development process significantly, especially for research software and prototypes.

GUIDO has been split into three consecutive layers: Basic
GUIDO introduces the main concepts of the GUIDO design and allows to represent much of the conventional music of today. Advanced GUIDO extends Basic GUIDO by adding exact score-formatting and some more advanced musical concepts. Finally, Extended GUIDO can represent user-defined extensions, like microtonal information or user defined pitch classes.

Example of GUIDO Input File

Source