Why Do Orchestras Tune to an A Note?


When orchestra members tune their instruments before a performance, it almost always sounds the same. That’s because across the world, most orchestras tune to the same A note, using a standard pitch of 440 hertz.

This is the result of international standards that have been in place since the 19th century, according to WQXR, a classical music radio station in New York City. Currently, standard tuning frequency is set by the International Organization for Standardization (ISO), an international group that makes recommendations on everything from what safety labels should look like to how big the hole in a pen cap should be. A standard called ISO 16, first recommended in 1955 and confirmed in 1975, “specifies the frequency for the note A in the treble stave and shall be 440 hertz.”

The ISO didn’t pull that frequency out of thin air. During the Industrial Revolution, a rush toward standardization and universality led to multiple international meetings that aimed to bring orchestras all over the world to the same pitch. Standardizing pitch had important ramifications for the international music scene.

Historically, the pitch that orchestras tuned to could differ wildly depending on where the musicians were playing. “In the course of the last 400 years in Europe, the point that has been considered ideal for a reference pitch has fluctuated by some 5 or 6 semitones,” musicologist Bruce Haynes explained in his book, A History of Performing Pitch: The Story of ‘A.’ In the 17th century, a French performer might tune his or her instrument a whole tone lower than their German colleagues. The standards could even change from one town to the next, affecting how music written in one location might sound when played in another.

As a writer for London's The Spectator observed in 1859, “It is well known that when we are performing Handel's music (for example) from the very notes in which he wrote it, we are really performing it nearly a whole tone higher than he intended;—the sound associated in his ear with the note A, being nearly the same sound which, in our ear, is associated with the note G.”

In the 19th century, a commission established by the French government tried to analyze pitch across Europe by looking at the frequencies of the tuning forks musicians used as their reference while tuning their instruments. The commission gathered tuning forks from different cities, finding that most were pitched somewhere around 445 hertz. Over the years, due to bigger concert halls and more advanced instruments, pitch was rising across most orchestras, and instruments and voices were being strained as a result. So the commission recommended lowering the standard to what was known as “the compromise pitch.”

In 1859, the French commission legally established diapason normal, the standard pitch for the A above middle C, at 435 hertz. (The music world would still be debating whether or not pitch had risen too much more than a century later.) Later, 435 hertz became enshrined as a standard elsewhere, too. In 1885, government representatives from Italy, Austria, Hungary, Prussia, Russia, Saxony, Sweden, and Württemberg met to establish their own international standard, agreeing on 435 hertz. The agreement was eventually written into the Treaty of Versailles in 1919.

But not everyone was on board with 435 hertz. The Royal Philharmonic Society in London believed the French pitch standard was pegged to a specific temperature—59°F—and decided to adjust their pitch upward to compensate for their concert halls being warmer than that, settling on 439 hertz. Meanwhile, in 1917, the American Federation of Musicians declared 440 hertz to be the standard pitch in the U.S.

In 1939, the International Standardizing Organization met in London to agree on a standard for concert pitch to be used across the world. A Dutch study of European pitch that year had found that while pitch varied across orchestras and countries, the average of those varied pitches was around 440 hertz. So it made sense for the ISO to choose A 440. Furthermore, radio broadcasters and technicians like the BBC preferred A 440 to the English A 439 because 439 was a prime number and thus harder to reproduce in a laboratory.

World War II delayed the official launch of the 1939 ISO agreement, but the organization issued its A 440 decision in 1955, then again two decades later. A 440 was here to stay. That said, even now, pitch does vary a little depending on the musicians in question. The Vienna Philharmonic Orchestra notably tunes to 443 hertz rather than the standard 440 hertz, for instance. While A 440 may be the official “concert pitch” across the world, in practice, there is still a little wiggle room.

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What Would Happen If a Plane Flew Too High?


Tom Farrier:

People have done this, and they have died doing it. For example, in October 2004, the crew of Pinnacle Airlines 3701 [PDF]  was taking their aircraft from one airport to another without passengers—a so-called "repositioning" flight.

They were supposed to fly at 33,000 feet, but instead requested and climbed to 41,000 feet, which was the maximum altitude at which the aircraft was supposed to be able to be flown. Both engines failed, the crew couldn't get them restarted, and the aircraft crashed and was destroyed.

The National Transportation Safety Board determined that the probable causes of this accident were: (1) the pilots’ unprofessional behavior, deviation from standard operating procedures, and poor airmanship, which resulted in an in-flight emergency from which they were unable to recover, in part because of the pilots’ inadequate training; (2) the pilots’ failure to prepare for an emergency landing in a timely manner, including communicating with air traffic controllers immediately after the emergency about the loss of both engines and the availability of landing sites; and (3) the pilots’ improper management of the double engine failure checklist, which allowed the engine cores to stop rotating and resulted in the core lock engine condition.

Contributing to this accident were: (1) the core lock engine condition, which prevented at least one engine from being restarted, and (2) the airplane flight manuals that did not communicate to pilots the importance of maintaining a minimum airspeed to keep the engine cores rotating.

Accidents also happen when the "density altitude"—a combination of the temperature and atmospheric pressure at a given location—is too high. At high altitude on a hot day, some types of aircraft simply can't climb. They might get off the ground after attempting a takeoff, but then they can't gain altitude and they crash because they run out of room in front of them or because they try to turn back to the airport and stall the aircraft in doing so. An example of this scenario is described in WPR12LA283.

There's a helicopter version of this problem as well. Helicopter crews calculate the "power available" at a given pressure altitude and temperature, and then compare that to the "power required" under those same conditions. The latter are different for hovering "in ground effect" (IGE, with the benefit of a level surface against which their rotor system can push) and "out of ground effect" (OGE, where the rotor system supports the full weight of the aircraft).

It's kind of unnerving to take off from, say, a helipad on top of a building and go from hovering in ground effect and moving forward to suddenly find yourself in an OGE situation, not having enough power to keep hovering as you slide out over the edge of the roof. This is why helicopter pilots always will establish a positive rate of climb from such environments as quickly as possible—when you get moving forward at around 15 to 20 knots, the movement of air through the rotor system provides some extra ("translational") lift.

It also feels ugly to drop below that translational lift airspeed too high above the surface and abruptly be in a power deficit situation—maybe you have IGE power, but you don't have OGE power. In such cases, you may not have enough power to cushion your landing as you don't so much fly as plummet. (Any Monty Python fans?)

Finally, for some insight into the pure aerodynamics at play when airplanes fly too high, I'd recommend reading the responses to "What happens to aircraft that depart controlled flight at the coffin corner?"

This post originally appeared on Quora. Click here to view.

Why Are Some Men's Beards a Different Color Than Their Hair?


Throughout civilization, beards have acted as a silent communicator. For some, it's a symbol of virility and power. For others, being hirsute is mandated by religion, marital status, or both. (Amish single men are clean-shaven; husbands are not.) Seeing an unkempt, scraggly beard could be an indication of a person's economic status or their lack of vanity. One man, Hans Langseth, sprouted a 17-foot-long chin warmer for the unique identity it afforded him. (He kept it neatly rolled over a corn cob when he wasn't busy showing it off.)

Langseth's whiskers, which wound up in the Smithsonian, present a curious timeline of his life. The furthest end of the beard was a vibrant brown, grown out when he was younger. The ends closer to his face—and to the end of his life in 1927—were yellowed.

While age can certainly influence hair and beard color, it doesn't explain why a younger man can sport a decidedly different beard tone than what's on the rest of his head. Other follicular forces are at work.

By default, scalp hair is white. It gets its color from melanin, turning it everything from jet black to dirty blonde. Pheomelanin infuses hair with red and yellow pigmentation; eumelanin influences brown and black. Like shades of paint, the two can mix within the same hair shaft. (Melanin production decreases as we age, which is why hairs start to appear gray.) But not all follicles get the same dose in the same combination. While you might sport a light brown top, your beard could be predominantly dark brown, or sport patches of lighter hairs in spots. Eyebrow hair will probably appear darker because those follicles tend to produce more eumelanin.

If you're wondering why these two-toned heads often have a red beard but not red hair, there's an answer for that, too. While all hair color is genetic, one gene in particular, MC1R, is responsible for a red hue. If you inherit a mutated version of the gene from both parents, you're likely to have red hair from head to toe. (Hopefully not too much toe hair.) But if you inherit MC1R from just one parent, it might only affect a portion of your follicles. If that swatch of color annoys you for whatever reason? There’s always beard dye.

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