Sound consists of regular vibrations in a liquid medium - usually air. When sound is organized into the patterns we perceive as music, it has three principle qualities: pitch, rhythm, and timbre (pronounced TAM-ber).
Pitch refers to the "highness" or "lowness" of a musical sound, ranging from the deep groan of the lowest notes of a double bass to the soaring heights of an operatic soprano's aria. Pitch is directly related to the frequency of the vibration in the air that carries the sound; slower vibrations are "heard" as lower sounds, and faster vibrations are perceived as higher sounds.
Pitch is measured in cycles (complete vibrations) per second, or cps. For example, the piano key "A above middle C" is normally turned to 440 cycles per second. In reality, the vibrations that make up sound are very complicated, and consist of a mix of several different frequencies. But usually a single frequency predominates, and this is the one we "hear."
One of the fundamental principles of musical pitch is that if one sound has exactly twice as many vibrations per second as another, then the sounds are perceived by the ear as "the same pitch" in a certain way. This allows men and women, for example, or adults and children, to sing together even when they have very different ranges of pitch that they can sing. The perceived "distance" between two such sounds, one being double the frequency of the other, is called an "octave." (This is our first example of a musical interval.)
Absolute and relative pitch
When performing music, we usually make a selection of the pitches to be played or sung; these pitches can be assigned names (A, B flat, and so on) and displayed on a musical staff, where each space or line represents a particular pitch; pitches with higher frequency at the top. Each of the round "dots" is called a note head.
When several musicians perform together, they usually need to tune their instruments or voices to an agreed-upon standard pitch, such as that produced by a tuning fork. This use of fixed pitches, agreed upon in advance, is called absolute pitch, and would be used, for example when church music is accompanied by an organ or other instrument. Absolute pitch is also used for classical music even when it is sung by voices alone, since the exact pitches employed may be critical to the sound of the resulting music.
But when folk music is sung, or church music without instrumental accompaniment, all that is needed is for the consecutive pitches in each voice (the melody) and the set of pitches sung by different voices at once (the harmony) have the right musical intervals between them. Usually, a starting pitch is chosen by one singer, or the others "tune" their singing appropriately. This is called relative pitch.
In our church, plain chant is almost always sung using relative pitch, with the priest or cantor selecting the beginning pitch.
To gain skill in distinguishing pitches, try out the Theta Music Trainer games Pitch Compare and Speed Pitch. In the Theta Music game Dango Brothers, you will learn to adjust one pitch to match another, and in Vocal Match you will sing back a pitch to match one you hear. All these are vital skills for cantors.
If pitch is the highness or lowness or a sound, rhythm describes the patterns of sound and silence, and the ways in which some sounds are emphasized more than others. Think of the regular sound of repetitive clapping, for example, or the pattern of a heartbeat. Musical rhythm can vary from extreme simplicity to great complexity, and some musical instruments (such as drums) operate almost entirely by marking rhythm.
When music is written down, different kinds of note heads show how long a sound is produced, and the other marks show intervals of silence, or which sounds are emphasized in various ways (by being played or sung with greater volume or greater intensity, using a different style, and so on). In most cases, there is a regular "beat" or rate of recurrence of sound, and the speed of this beat is called tempo.
Like pitch, rhythm can be absolute or relative. To duplicate a rhythm exactly, one can use very specific musical notation, and control the tempo using a tool such as a metronome. If exact reproduction is not necessary, then a relative rhythm can be obtained by picking one of the note durations as a standard, and adjusting the lengths of the rest of the sounds accordingly.
The Theta Music Trainer includes a number of games to teach you to read musical notation for rhythms.
The music of spoken language
We usually think of singing as a different sort of "thing" from spoken language. But spoken language includes variations of pitch and tempo, just like singing. This is easy to demonstrate: when words are spoken on the exact same pitch, we call this a monotone or say that it sounds like a machine speaking, and if we speak words in an exact unvarying rhythm, we say that it sounds mechanical. Human language incorporates many small variations in pitch and rhythm, and each language uses pitch and rhythm in particular ways. (For example, in English, rising or falling pitch can distinguish a question from a statement or a command.)
Because our church plain chant is really sung speech, it too employs small variations in pitch and rhythm, to suit the meaning of the words being sung.
The complex vibrations of natural sound result in wide variations in how a sound is "heard", even when the pitch and rhythm are the same. For example, a violin, clarinet, and piano will sound very different even when they play a note of the exact same pitch and duration. The different sound of each instrument is its timbre.
Timbre can also change with the way music is performed; for example, the timbre of the voice will change depending on how the singer stands, breathes, and sings. There is no standard notation for timbre, but singers need to be alert to it in order to make their singing as attractive as possible; some aspects of timbre can also draw the attention of the listener, and are useful when leading the singing of others. On the other hand, the ability to adjust the timbre of one's own singing to allow the singing of different voices to combine well is called blend.