Unison
0 semitones — two notes at the same pitch
Degree 1Solfège: doNotation: P1
The unison is two notes at the same pitch — an interval of 0 semitones, also called the prime. It is perfectly consonant: the most stable relationship possible, since the two notes are identical. More a reference point than an interval in practice, it is the root from which all others are measured.