Before every concert the same scene unfolds. The orchestra is seated, the first violin stands up, looks towards the winds, and an oboe plays a long note. Everyone tunes to that. Nobody ever explains why it falls to the oboe, and the reason has nothing to do with the beauty of the sound: it is a matter of how the instrument is built.
The oboe is the most rigid instrument in the orchestra. A violin is tuned by turning the pegs, and in thirty seconds you have it where you want it. A flute has a head joint that slides out and in, and with that movement you raise or lower the overall pitch. A clarinet has interchangeable barrels. The oboe does not. The oboe’s pitch depends almost entirely on the double reed, that is, on two blades of cane that the oboist makes for himself, and there is no mechanical gadget to shift it appreciably. In practice it is the instrument with the least margin of all. So it dictates, and the others adjust, because moving twenty-seven people who can move costs less than moving one who cannot.
There is a second reason, and it is acoustic. The oboe’s sound has a spectrum rich in upper harmonics and a sharp attack, so it stands out in the noise of sixty people arranging chairs and turning pages. A flute note in that situation is hard to hear, an oboe note you hear from the back of the hall.
The note is A, and it is the note needed first of all by the strings, which all have that sound on an open string: A is an open string on violin, viola, cello and double bass. From there everyone tunes the other strings, in fifths on the three instruments of the violin family and in fourths on the double bass, and in thirty seconds the problem is solved.
How high that A is, however, is not a stable fact at all, and it is one of the few things in music on which Europe has never agreed. In the seventeenth and eighteenth centuries every city had its own, measured on its organs, and the differences reached a whole tone: there were very high German organs and Venetian instruments considerably lower. Those who play early music today conventionally use an A around 415 hertz, which compared with ours is almost a semitone lower, but that is a convenient modern convention, not a historical truth.
The first serious attempt to put order into this is French and has a date. In 1859 a government commission fixes by law the standard diapason at 435 hertz, and France imposes it on the theatres. The reason is not aesthetic but a trade-union one, that is, it is the singers who push for it: the higher the pitch rises, the more the parts written fifty years earlier become tiring, and the repertoire wears out on the voices.
In the twentieth century we arrive at 440, sanctioned by international agreements and then by an ISO standard in the 1950s. But that standard has never really been respected. Several European orchestras today play at 442, and some, in the Austro-German area, go towards 443 and beyond. The declared reason is the brilliance of the sound, and the undeclared consequence is that the nineteenth-century repertoire is performed higher than it was written.
Verdi thought differently and had come late to the matter. In 1884 he asked for, and obtained, the official adoption in Italy of an A at 432 hertz for orchestral instruments, a figure that originated in the French proposal. The standard stayed on paper, like almost all standards in this area. From there also derives a contemporary legend, that of 432 as a natural and beneficial frequency, which has nothing to do with Verdi: all he wanted was to stop making his tenors sing a semitone above what was intended.
So, back to the opening scene: when the oboe gives the A, it is giving a number decided by someone. In France in 1859, in London in 1939, in Italy never really. And every time that number has gone up, someone on stage has had to sing higher than the composer had foreseen.