Music is created from pitches, specific points on the spectrum of sound frequency which we measure in Hertz. Octaves are distances between pitches where the frequency of the second pitch is twice the frequency of the first. Western music divides octaves into twelve equally-spaced pitches. These twelve pitch relationships and their interactions with one another form the basis of all Western music.
White notes on the keyboard are named with the letters A–G, starting with the first key and repeating the length of the keyboard. Black notes are named in reference to white notes, using either a flat (b) or sharp (#) after the white key’s name to signify the note directly below or above, respectively. The repeating pattern of black and white keys is twelve notes long.
Notes on the keyboard can also be identified by their register — which part of the keyboard they belong to — by numbers following their names. The first register begins at the lowest C on the keyboard.
The A above the middle C on the keyboard (A4) is tuned to 440 Hz. Every other note relates to this by intervals of octaves and their twelve divisions, which we call semitones. Every note on the keyboard is a semitone from the next note, and any twelve consecutive notes (beginning anywhere on the keyboard) cover the distance of an octave. Every note twelve notes apart share a name and relate to each other by an octave. Consequently, each note of the keyboard has a specific assigned pitch.
A scale is a repeatable series of selected semitones across an octave, defined by the distances from each pitch to the next. The most commonly used scales in Western music consists of seven pitches, arranged in specific patterns of semitones and tones (the distance of two semitones). For example, all major scales consist of the pattern tone-tone-semitone-tone-tone-tone-semitone between pitches. When we play this formula beginning on any note of the keyboard, we are playing that note’s major scale.
Scales can be identified by their type — the specific pattern of intervals between their pitches — and by their starting note, or “root” note. For example, if we play the pattern tone-tone-semitone-tone-tone-tone-semitone beginning on the note of C, we will create a C major scale. However, if we move each pitch down a tone, the starting note will change, and it will become a Bb major scale. In this case, the actual pitches change, but the relationships or intervals between them stay the same, and the character of the scale is preserved.
If instead we start our scale on C, but change the pattern of pitches to tone-semitone-tone-tone-semitone-tone-tone, it will become a C minor scale. This scale has the same root note as a C major scale, but the relationships between the pitches change, and the character of the scale is altered. Any type of scale (major, minor, mixolydian, whole tone, etc.) can begin on any note.
Each major or minor scale comprises the notes of a corresponding key, named from its root note. The root, also called the tonic, is the tonal center of the key. Notes of the key are often referred to by their scale degrees (their numerical order in the scale), and have a distinctive relationship with the tonic note. Music typically emerges from and returns to the tonal center in some form, and it provides context through which to interpret the other note relationships.
Music is, by nature, relational. The specific pitches used within music matter much less than the relationships between those pitches. This is why a song still sounds recognizable when it’s sung using a different starting note than the original version. Understanding how pitches relate to one another, either consciously or intuitively, is fundamental to expressing something meaningful and effective through music. Just as understanding the distinct parts of speech, either consciously or intuitively, is fundamental to expressing oneself through language regardless of specific words; understanding relative functions within music is essential for coherent expression.