When layer lines were first introduced, we saw that they represent not only a certain amount of time flowing from left to right, but also 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 (see Unspecified pitch).
Another example of an element that might be considered to continue through time in a piece of music, as an ever-present possibility if not actually manifested at every moment, is a particular musical pitch. Most music uses certain pitches repeatedly though not constantly, so that such pitches endure through time at least in the sense of being “kept in mind” when not actually sounding. Accordingly, when pitch is to be specified in a score, a continuous horizontal line can be used to represent a recurring pitch (rather than representing a “layer” as when pitch is unspecified). This is the basis of Global Notation’s approach to specifying pitch.
A continuous horizontal line that represents a particular pitch will be called a “pitch line.” It may look like a layer line, but in practice it will be readily distinguishable by the fact that symbols are usually placed on a pitch line rather than immediately above and/or below it. (More precisely, the vertical centre of the symbol is normally aligned with that of the pitch line.) A symbol placed on a pitch line indicates a sound of the pitch represented by that line.
The symbols placed on a pitch line may be for sounds of either specified or unspecified duration (see Specified duration). Most xylophone sounds are of definite pitch but rapid decay, so it will usually make sense to specify their pitch but not their duration. Most sung, blown, and bowed sounds are of definite pitch and are (within limits) sustainable, so it will usually make sense to specify both their pitch and their duration.
Music based on a monotone, such as an Australian didjeridu solo, could be notated on a single pitch line.
Incidentally, since the layer line for the didjeridu is almost entirely hidden by the symbols for sounds of specified duration, this might be a case for writing the symbols in grey or in a colour (see Specified duration).
(As it isn’t entirely clear in this example how - or whether - the beats are grouped into bars, no bar lines are shown, and no figure is given for the number of beats per bar, though as you can see, this does not prevent our specifying the division of beats. The pulsation in the volume of the didgeridu sound is not represented either, as we don’t yet have the means to do that; see Dynamics and accentuation.)
Though optional (as always), we may well wish to specify what pitch is being used. In the case of a monotone, we cannot compare it with other pitches in the same piece, so we can only measure the pitch by some yardstick external to the piece. That is to say, we can specify the pitch in absolute terms.
One way of specifying absolute pitch is to measure the frequency in vibrations per second, or Hertz (Hz). This is easily done using open-access sound analysis software. Hertz figures, however, don’t convey much to most people, even to trained musicians, and it will probably be more helpful to specify absolute pitch in relation to a widely accepted pitch standard, that of “concert pitch.”
In concert pitch, the pitch called A4 is defined as having a frequency of 440Hz, and all the other pitches are derived from that.
Pitch names such as A4 are based on counting the “Cs” on a standard piano keyboard, starting from the lowest one. For example, the fourth-lowest C, commonly known as “middle C,” is C4. The white notes immediately above that are D4, E4, and so on.
After G4 the alphabetical sequence resumes with A4 and B4, but the number doesn’t go up to 5 until you get to the next C. (This has to do with the fact that the major scale starting on C is considered the most basic one, as it doesn’t require any black notes.) When a piano is tuned to concert pitch, A4 is set at 440Hz and all the other notes from A0 to C8 are tuned to be the right amount higher or lower than that.
Of course, the pitches on a piano keyboard are not the only ones used in the world’s music: they are just one set of gradations along a pitch continuum, like the marks for centimetres or inches on a ruler. So long as you remember that, they do provide a useful way of specifying absolute pitch in relation to a measuring stick that is familiar to many musicians the world over.
Any pitch that you want to specify in absolute terms can be approximated to the nearest pitch available on a piano keyboard. If the pitch stated is only an approximation, it is preceded by the mathematical sign for “approximately equal to,” ≈.
If you like, you can also specify exactly how close the pitch is to the nearest one on the keyboard (see Relative pitch). You can even use a diagram of a keyboard to represent the pitch more graphically.
Specifying absolute pitch is the equivalent of telling the reader what “key” the music is in. In global notation, a single indication at the beginning of the score is enough to do this, and our attention can then be devoted to what is usually far more musically significant: the relationships among the various pitches within a piece of music, which we call “relative pitch.”
Sources of audio
Didjeridu played by Peter Manaberu on “Jabiru” from Wangga Songs by Alana Maralung, Smithsonian Folkways CD 40430 (1988), track 5.