A perfect octave is a musical interval that spans eight diatonic scale degrees. It occurs when the frequency of one note is double that of another note. For example, if the note C has a frequency of 261.63 Hz, the note C one octave higher will have a frequency of 523.25 Hz. This interval is considered one of the most consonant and harmonious in music. In Western music, perfect octaves are represented by the same letter name, such as C to C or G to G. They are fundamental in creating scales, chords, and melodies, serving as a building block for various musical compositions.