# 6. Definitions of terms¶

- Cent
- Twelve-tone equal temperament divides the octave into 12 semitones of 100 cents each.
- Just intonation
- Just intonation or pure intonation is any musical tuning in which the frequencies of notes are related by ratios of small whole numbers.
- Middle C
- The fourth C key from left on a standard 88-key piano keyboard is designated C4 (SPN) (Do3).
- Octave
- See Scientific Pitch Notation for numbering.
- Pitch
- The property of a musical tone that is determined by its frequency
- Pitch Class
- For example, the pitch class “C” is the set {Cn : n is an integer} = {…, C−2, C−1, C0, C1, C2, C3 …}
- Quality
- The name of any interval is further qualified using the terms perfect (P), major (M), minor (m), augmented (A), and diminished (d).
- Semitone
- A semitone, also called a half step or a half tone, is the smallest musical interval commonly used in Western tonal music. It is defined as the interval between two adjacent notes in a twelve-tone equal temperament.
- Scientific Pitch Notation (SPN)
- According to the Scientific Pitch Notation, A4 corresponds to a tone of frequency 440 Hz, note A and octave 4. A4 corresponds to La3 in Latin notation, where the octave bellow 1 is -1. The MIDI specification range from C-1 to G9.
- Step
a degree, grade, or rank in a scale

the interval between two adjacent notes in a musical scale

- Tone
- …