Unison (prime)

Two equal notes

The page Intervals describes the prime as the sound together of two identical notes. It counts as the most perfect of all consonances: there are no beats, no friction and no tension. Both notes vibrate at the same frequency in the ratio 1:1 and fuse into a single, undivided sound.

In music theory the unison is the starting point of all interval formation. According to the home page, you count in steps of the letter names, from the unison through second, third, fourth, fifth, sixth and seventh to the octave. The unison produces no harmonic movement, but it supplies the point of rest from which every melodic or harmonic journey begins and to which it ideally returns.

Unison: when everyone plays the same note

The Intervals page describes where the prime occurs in practice: when several voices or instruments play the same note to reinforce a melodic line (unison) or to blend a timbre by doubling, for example violin and flute on the same note. The page Klang-Spektrum gives an example of how differently doublings work: two flutes in unison sound like one instrument, two oboes remain two oboes.

The prime also occurs in singing. The page German Song Sheets describes a chorale sung in unison: if a group sings “Nun danket alle Gott” in unison and hears the setting on the piano with it, it doubles the soprano. According to the page that sounds good and is perfectly fine.

The article Using a capo properly shows the opposite case: two guitars in G, one without a capo and the other with the capo at the seventh fret in a C shape, both sound in G, but in different registers. That gives a two-part accompaniment with a real difference in sound instead of a doubled unison.

The unison on the guitar

On the guitar the unison is an open string. Nothing is fretted, the string vibrates at full length. The string-length ratio is 1/1. On the high E string the sound stays at 329.63 Hz, according to the Intervals page the lowest frequency this string can produce. Every further note arises by shortening the vibrating length. The unison also sounds when you tune two strings to the same note, for example when tuning by ear: if they do not agree, you hear beats.

Common mistakes

• Treating the unison as nothing: According to the Intervals page it is no interval in the strict sense, but the sound together of two identical notes, yet it is counted as the first degree.
• Confusing unison and octave: The octave sounds like the same note at a different pitch, the unison really is the same note.
• Confusing playing in unison with identical tuning: Two “equal” notes can be slightly out of tune. Then they beat, and the unison does not sound pure.