C.1.2 Internal music representation

When a music expression is parsed, it is converted into a set of Scheme music objects. The defining property of a music object is that it takes up time. Time is a rational number that measures the length of a piece of music, in whole notes.

A music object has three kinds of types:

• music name: Each music expression has a name, for example, a note leads to a NoteEvent (lilypond-internals), and \simultaneous leads to a SimultaneousMusic (lilypond-internals). A list of all expressions available is in the internals manual, under Music expressions (lilypond-internals)expressions.
• `type' or interface: Each music name has several `types' or interface, for example, a note is an event, but it is also a note-event, a rhythmic-event and a melodic-event.

  All classes of music are listed in the internals manual, under Music classes (lilypond-internals).

• C++ object: Each music object is represented by a C++ object. For technical reasons, different music objects may be represented by different C++ object types. For example, a note is Event object, while \grace creates a Grace_music object.

  We expect that distinctions between different C++ types will disappear in the future.

The actual information of a music expression is stored in properties. For example, a NoteEvent (lilypond-internals) has pitch and duration properties that store the pitch and duration of that note. A list of all properties available is in the internals manual, under Music properties (lilypond-internals).

A compound music expression is a music object that contains other music objects in its properties. A list of objects can be stored in the elements property of a music object, or a single `child' music object in the element object. For example, SequentialMusic (lilypond-internals) has its children in elements, and GraceMusic (lilypond-internals) has its single argument in element. The body of a repeat is in element property of RepeatedMusic (lilypond-internals), and the alternatives in elements.

This page is for LilyPond-2.2.6 (stable-branch). Report errors to <bug-lilypond@gnu.org>.