A440
Authority: ISO 16:1975 Acoustics Standard
ISO 16 standardizes A above middle C (A4) to exactly 440.00 Hz as the international orchestra tuning standard. Scientific (Verdi) tuning sets C4 to 256.00 Hz, placing A4 at 430.54 Hz.
| Parameter / Specification | Standard Value | Unit |
|---|---|---|
| ISO 16 Concert Pitch A4 Frequency | 440.00 | Hz |
| Middle C (C4) at A440 Equal Temperament | 261.63 | Hz |
| Scientific Pitch Middle C (C4) | 256.00 | Hz |
| Scientific Pitch A4 Equivalent | 430.54 | Hz |
History & Origin
Before the 20th century, there was no single agreed concert pitch -- orchestras across Europe tuned to noticeably different frequencies, with France formally adopting A=435 Hz (the 'diapason normal') in 1858 while other countries used their own references, often creeping upward over time as instrument makers and orchestras chased a brighter sound. The push toward a single global standard culminated in a May 1939 conference at the BBC's Broadcasting House in London, attended by delegates from Britain, France, Germany, the Netherlands, and Italy, with Switzerland and the US participating by telegram. The conference settled on A=440 Hz, a value already in use by the American Standards Association since 1936 and by the BBC for its broadcast tuning signal.
The International Organization for Standardization formally adopted 440 Hz as ISO Recommendation R16 in 1955, later codified as ISO 16. Scientific (Verdi) pitch, which sets middle C to exactly 256 Hz -- a physically convenient value since it is a power of two -- was an earlier, competing reference proposed in the 19th century that never displaced A440 as the practical orchestral standard.
Related Pages
Referenced By
Banjo
Standard 5-string banjo Open G tuning, thickest to thinnest full-length string: D3, G3, B3, D4 (4th to 1st string), plus a short 5th drone string tuned to G4 -- higher than every other string. At A440 concert pitch these are 146.83 Hz, 196.00 Hz, 246.94 Hz, 293.66 Hz, and 392.00 Hz.
Comparison TableMandolin
Standard mandolin tuning matches violin pitch, G3-D4-A4-E5, but each note is doubled into a two-string course tuned in unison, producing the instrument's characteristic bright, shimmering tone. All four courses are tuned in perfect fifths, the same interval pattern as a violin.
Comparison TableBass Guitar
Standard 4-string bass guitar tuning is E1-A1-D2-G2, exactly one octave below the bottom four strings of a standard guitar. At concert pitch, the frequencies are E1 41.20 Hz, A1 55.00 Hz, D2 73.42 Hz, and G2 98.00 Hz.
Comparison TableViola
Standard viola tuning uses four strings in perfect fifths, low to high: C3, G3, D4, and A4. At A440 concert pitch these correspond to 130.81 Hz, 196.00 Hz, 293.66 Hz, and 440.00 Hz -- one perfect fifth below the violin's tuning and one octave above the cello's.
Comparison TableViolin
Standard violin tuning uses four strings in perfect fifths: G3, D4, A4, and E5. At concert pitch, A4 equals 440 Hz, these correspond to 196.00 Hz, 293.66 Hz, 440.00 Hz, and 659.25 Hz. Unlike guitar, violin strings are single courses with no doubled strings.
Comparison TableGuitar
Standard 6-string guitar tuning (E2-A2-D3-G3-B3-E4) fundamental frequencies: 6th String E2 (82.41 Hz), 5th String A2 (110.00 Hz), 4th String D3 (146.83 Hz), 3rd String G3 (196.00 Hz), 2nd String B3 (246.94 Hz), 1st String E4 (329.63 Hz).
Comparison TableCello
Standard cello tuning uses four strings in perfect fifths, low to high: C2, G2, D3, and A3. At A440 concert pitch these correspond to 65.41 Hz, 98.00 Hz, 146.83 Hz, and 220.00 Hz -- the same pitch classes as the viola, just one octave lower.
Comparison TableUkulele
Standard soprano and concert ukulele tuning is G4-C4-E4-A4, a re-entrant tuning where the G string is pitched higher than the C and E strings below it. At concert pitch, the frequencies are G4 392.00 Hz, C4 261.63 Hz, E4 329.63 Hz, and A4 440.00 Hz.
Comparison TableDouble Bass
Standard orchestral double bass tuning uses four strings tuned in perfect fourths -- not fifths like the rest of the violin family -- low to high: E1, A1, D2, and G2. At A440 concert pitch these correspond to 41.20 Hz, 55.00 Hz, 73.42 Hz, and 98.00 Hz.