Octave
An interval spanning seven diatonic degrees or eleven semitones. An octave above C would be C. The frequency of a note one octave above another will have exactly twice as many Hertz as the frequency of the note an octave below it.
Degree
The tones of the diatonic scale. The first degree of the scale is the tonic, the second is the supertonic, the third is the mediant, the fourth is the subdominant, the fifth is the dominant, the sixth is the submediant, the seventh is the leading tone.
Semitone
A half step; a minor second; the smallest interval in the system of Western music.
Note
A notational symbol used to represent the duration of a sound, and when placed on a music staff, also indicate the pitch of the sound.
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