There are some terms commonly found in discussions of music notation which most musicians intuitively understand. This section defines the specific usage of these terms in NIFF.
There are two types of time-slice: measure start and event. The measure-start time-slice identifies the start time of a measure with respect to the start of the score. The event time-slice identifes the start time of an event such as a note or rest with respect to the start of the measure.
The NIFF logical structures were designed to handle situations like the following:
Example 1. In a Mahler symphony score there are three trumpet parts. In one system the trumpets appear on three separate staves (labelled "Tpt. 1", "Tpt. 2", Tpt. 3"), because they are playing a complex canon. In another system they appear all together on one staff, called "Tpts. 1,2,3," because they are playing homophonic music. They are written as chords, with 3 notes on one stem.
In the logical view, the notes played by the trumpets belong to three separate parts.
In the physical view of the canonic system, each trumpet part is assigned its own staff. Each staff is labelled with its own name.
In the physical view of the homophonic system, the three parts are combined together onto a single staff, labelled "Tpts. 1, 2, 3." The simultaneous notes of each chord played by the three trumpet parts appear together with a single stem within each time-slice. Each note indicates the part to which it belongs.
Example 2. Consider a score with divisi writing where the first violin part is temporarily divided into groups. The first violin part is split onto two separate staves in one system, and three separate staves in another system. There are a variety of ways this could be represented in NIFF. The choice depends on the desired result when the parts are to be extracted and printed for individual players:
a) If the first violin part score is to show all the divisi parts, the first violin should be defined as a single part with three voices and a maximum number of staves of three. The notes of this part would be distributed among the one, two or three active voices, each voice presented on its own staff.
b) If separate part scores are to be printed for different first violin players, more than one first violin part should be defined in the NIFF file. All the musical symbols that are to be printed on a particular part score would have that part number indicated. If the same passage is to be printed on two different part scores, both part numbers should be indicated for each symbol within the passage.