1/1

Interval information

Ratio	1/1
Factorization	n/a
Monzo	[0⟩
Size in cents	0¢
Names	(perfect) unison, (perfect) prime, 1st harmonic, 1st subharmonic, fundamental
Color name	w1, wa unison
FJS name	[math]\text{P1}[/math]
Special properties	reduced, harmonic
Tenney height (log2 nd)	0
Weil height (log2 max(n, d))	0
Wilson height (sopfr(nd))	0
Harmonic entropy (Shannon, [math]\sqrt{nd}[/math])	~1.19982 bits
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English Wikipedia has an article on:

Unison

The unison (interval ratio 1/1) is the interval between two tones that are identical in pitch. In the harmonic series, 1/1 is the 1st harmonic, and likewise in the subharmonic series 1/1 is the first subharmonic- this is because it acts as the fundamental to both series.

Measured in cents (or any other logarithmic measure such as millioctaves, EDO steps, etc.), the unison's size is exactly 0. This is because the distance between two identical pitches is zero. As such, the unison can be considered as a degenerate interval.

In just intonation, 1/1 represents the base frequency from which an interval is measured.

See also

• Octave
• Octave reduction