Musical scores abound with ambiguous notations for dynamics, tempo, and other musical elements. To automatically generate a MIDI or other sound file, some value must be used for dynamics or tempo. MusicXML defaults to a MIDI velocity of 90 (roughly a forte); no default tempo is specified.
Sound suggestion elements and attributes guide the creation of a sound file. Most of the sound suggestions are found in the sound element, defined in the direction.mod file. Tempo is specified in quarter notes per minute. Dynamics are specified as a percentage of the standard MusicXML forte velocity. For example, the following sound element specifies a tempo of quarter note = 88 with a MIDI velocity of 64:
<sound tempo="88" dynamics="71"/>
The other attributes for the sound element are described in the direction.mod file. Sound suggestions are also available for grace notes (the steal-time-previous, steal-time-following, and make-time attributes, defined in the note.mod file) and for ornaments (the trill-sound entity for trills and other ornaments, defined in the common.mod file).