Why do instruments get tuned according to an A?
We are so used to tuning to an A that we no longer question why...is the reason scientific? Or perhaps out of convenience? No, in fact we use it by convention.
Before a concert, it is always an A, more precisely an A above middle C (the one written between the second and the third line of a stave) that tells us to stop talking. The instruments are being tuned. The conductor is about to come on stage.
The A above middle C is the empty string that the violin and the viola have in common. But, if those instruments can be tuned easily, with only a few turns of the peg, they are also extremely sensitive to temperature changes and therefore need to be frequently readjusted. Thus it is the oboe, requiring more time to be tuned, that gives the A to the string instruments and to the other sections.
And this famous A reaches far beyond the orchestra: it is the tuning of all Western music. Which means it is the reference point most commonly used to tune instruments and voices.
From physics to music
Yes, but to what frequency must we set this famous tuning? Because, if some orchestras use an A at 440 Hertz (meaning 440 vibrations per second), others, such as medieval and baroque music ensembles, use an A set at 415 Hertz.
Why an A at 415Hz for baroque music? Was this the tuning used at the time? The question is in reality anachronistic since the concept itself of frequency was discovered only in the 18th century. And before 1930, we didn't talk about Hertz (Hz) but about cycles per second.
An A for everyone
Until the 19th century, the tuning didn't exist (at least, in the way that we understand it today as a fixed note of reference). The instruments were tuned according to one another. For example, they were tuned according to the flutes, as their range is fixed.
Every musician knows how to transpose, to adapt to the context in which he is performing. The tuning therefore changes according to the geographic spaces but also within the same space: the "chapel tone" is for example rather low, to facilitate the singing, whereas the "chamber tone" of the orchestra rings higher.
One tuning for all and all for one tuning
The diversity of tunings in circulation was a problem for the travelling musicians. How could one play in unison with instruments of another make? How can one adapt their ear to a completely different tone? As the exchanges between musicians became more intense, the idea of a greater uniformity began to gain popularity...
Finally, a unique tuning was gradually imposed during the 19th century, in particular as a result of the first industrial revolution and the birth of serial production. More and more instruments were produced and sent all over the world. It therefore became possible to use the same flute or trumpet in Berlin and in Milan.
To save the singers
In the 19th century, a far-reaching movement rose in defense of a unique tuning, from both musicians and the makers. Imagine for a second a French soprano invited to play The Queen of the Night in Covent Garden only to discover that her two virtuoso arias are performed at an A higher than the one in use in Paris. Her famous high-A could be in great danger...
Some singers and composers therefore joined the movement in favour of a standardisation of the A. It was the case of Verdi and Berlioz, the latter even writingto a minister that he was "convinced with reason that the progressive elevation of tuning is a cause of ruin for the greatest voices".
If the treatises and studies of the period instruments show that the A could reach 300 or 560 Hertz between the 16th and the 19th century, this note did indeed have a tendency to go higher during the period of Verdi and Berlioz.
Why? In theory, the higher an instrument's tuning, the more brilliant its sound. In practice, however, raising the A came as a result of the introduction of steel strings, able to provide the necessary sonority required by orchestras to adapt to venues continuously growing in size.
The time for normalisation
Facing this large variety of tunings, the French government gathered in 1858 a commission of physicists and musicians, including Berlioz, Auber, Meyerbeer and Rossini. After a year of work and research, the A above middle C was set in France at 435Hz.
The initiative was inspiring but remained exclusive. It was only in 1939 that the famous A 440 was declared as the international reference by a group of experts, in London. It would become an ISO standard and even a European recommendation.
Why 440? Some say it matches the European average. Other say that it was adopted because the instrument makers began exporting to the United States, where the tuning was higher, due in particular to the influence of jazz.
Ultimately, the use of the A 440 is not mandatory. Every musician is free to choose their own tuning!