Having decided whether to specify our sound sources, we next need to decide what “layers” to put them into, and what form these layers should take. In effect, we are now preparing the “manuscript paper” on which our symbols for sounds will be written. As also happens with conventional staff notation, the manuscript paper takes different forms depending whether pitch is being specified or not.
“Pitch” means how high or low the sound is, or more technically, how fast are the vibrations in the air that we perceive as sound. For a definite pitch to be perceived, the vibrations must be sufficiently regular. If they are not, we hear a sound of indefinite pitch.
If the sound has no definite pitch, as with many drums and other percussion instruments, then pitch should be unspecified in the score. However, the distinction between definite and indefinite pitch is not always clear, and there may sometimes be reasons for leaving pitch unspecified even if the sounds are of definite pitch.
If we have decided to leave pitch unspecified, the basic form of the manuscript paper is a continuous horizontal line that represents a certain amount of time flowing from left to right. This line also represents some element that is considered as continuing through time even if it is not always audible in sound, such as the “part” played by an individual musician who remains present in the ensemble even when not actually playing.
There will often be more than one of these horizontal lines, stacked one above another in layers that correspond to simultaneous “layers” of sound, such as the parts played by different instruments in an ensemble.
We will refer to such a line as a “layer line.” A group of layer lines representing simultaneous layers of sound, or a single layer line if only one layer of sound is being notated, is called a “system.” On reaching the end (i.e., the right-hand edge) of a system, a new system is started below it, just like starting a new line in ordinary writing.
Systems on the same page are separated from each other by a “system break” sign resembling a double slash: //. The identification of sound sources (or other information as to what each horizontal line represents) need only be given in the first system, unless there is potential for confusion, for instance when there are many layers or some of them don’t appear in every system.
A layer in which pitch is to be specified will take a different and more complex form, which is explained on a separate page and best studied later (see Specified pitch).
For now, the distinction between specified and unspecified pitch can be your guide as to what layers to use in your score. In general, sounds of unspecified pitch are most clearly notated by using a separate layer for each sound source, as in the above examples. Sounds of specified pitch, in contrast, are most efficiently notated by combining all such sounds in the smallest possible number of layers - ideally just one.
Therefore, if your score is to include sounds of both specified and unspecified pitch (for instance, if the music includes sounds of both definite and indefinite pitch, and you want to distinguish the two), then a good rule of thumb is to begin with one layer for all sounds of specified pitch plus one layer for each sound source of unspecified pitch.
Before dealing with the more complex matter of specifying pitch, we can now use our “manuscript paper” for layers of unspecified pitch to introduce the use of Global Notation’s basic symbols for sounds.