Specified onset timing
We have considered reasons for and against specifying sound sources, pitch, and duration in various situations (see Sound sources, Unspecified pitch, Unspecified duration). But one thing that we will nearly always want to specify about musical sounds is when they happen. In speech and ordinary writing, what matters is basically the order in which the sounds happen, but in music it’s also important how far apart they are in time.
Above all, what matters is when each sound begins, which we will call its “onset timing.” Even in music without a regular “beat,” onset timing is usually so vital to the effect that it is worth specifying with some precision.
It’s true that not all traditional forms of notation do this; for instance, Gregorian chant notation and many Asian notations only specify the order of sounds, not their length or timing. That doesn’t mean that timing is unimportant in those forms of music, but rather that it is guided by other things than notation; for instance, by the natural speaking rhythm of the words, by the performer’s memory and familiarity with the style, and in general by the “oral” part of the tradition.
However, when working across traditions, as Global Notation is designed to do, these forms of guidance tend to be less available, and the information they would provide within their own tradition is often worth incorporating into the score.
Like all other parameters, onset timing can be left unspecified in Global Notation if preferred. That might be appropriate, for instance, if you are transcribing some music from a traditional notation that doesn’t specify timing and you only want to include the information that is in the original source. In most other situations, however, we will assume that onset timing is to be specified.
It is important to remember that onset timing is not the same as duration. A sound does not necessarily continue until the onset of the next sound from the same source, so the length of time between the onsets of two successive sounds should not be equated with the duration of the first sound. Nor does the insertion of “rests” between the two sounds necessarily solve the problem, since it still requires one to specify the duration of the first sound—which, in the case of impulsive sounds, can be a moot point, as we’ve seen (see Unspecified duration).
Staff notation specifies onset timing only indirectly, by means of symbols that directly specify the durations of sounds and silences - “notes” and “rests” respectively. But as Global Notation allows for the option of leaving duration unspecified, it must specify onset timing independently of duration. This also has the advantage of making “rests” unnecessary: where there is no sound, nothing need be written.
Separating onset timing from duration allows Global Notation to represent rhythm in the way we usually hear it: not as an adding-up of durations, but as a series of sound-events (chiefly onsets) in relation to a steady beat or pulse. However, not all music has a regular pulse, so Global Notation provides ways of specifying onset timing both with and without a pulse.
For simplicity, the specification of onset timing is introduced here using examples with unspecified pitch only. The same principles will be applied in contexts of specified pitch after the specification of pitch has been introduced.