What is an "octave"?

An octave is defined as the interval between one musical pitch and another pitch that has a frequency relationship of 2:1, meaning that the higher pitch vibrates at twice the frequency of the lower pitch. When we refer to notes with the same letter name being an octave apart, we are capturing this essential quality of pitch in music.

For instance, if one note is a C, the next C that is an octave higher has double the frequency of the first C, thus creating a familiar sound relationship that is foundational in music. This relationship is integral in many musical compositions and scales, making it a crucial concept for understanding music theory and harmony.

In contrast, while the interval between two pitches is related, identifying it strictly by 'similar frequency' does not encapsulate the specific nature of an octave, which is defined by the exact doubling of frequency. Similarly, describing it as a part of a musical scale does not highlight its uniqueness compared to other intervals, and characterizing it as a singing technique misconstrues the term entirely.