Why is A4 the standard pitch reference for tuning?

Question

Why do musicians use concert A, the A above middle C, as the standard pitch reference for tuning? Various national and international standards define the frequency of this note. For example, ISO 16 specifies that musical instruments should be tuned such that A4 is 440 Hz. Other standards specify A4 as 415 Hz, 435 Hz, and various other values. Wikipedia does a good job of explaining why they chose the various frequencies, but why do they define that particular note as the tuning standard?

A few standards do use other reference pitches, like scientific pitch with C4 = 256 Hz, but the vast majority define A4. Likewise, some kinds of bands tune to other notes, like B♭ for wind bands, but again most use A. Why? Wikipedia suggests that it’s because all orchestral stringed instruments have an A string. Is that the whole reason, or are there other factors?

Answer 1

Had to do some digging for this one.

First off, some informed speculation:

A, of course, is the first letter in the alphabet, so its as good a place as any to define a standard. Plus, as you say, it is one of the open strings in common on all string instruments (along with D and G). The A above middle C is also a relatively centrally-located pitch, accessible to a range instruments. An octave lower would have been inaccessible to flutes and oboes (and not an open string).

To expand on this: String instruments are relatively easy to retune, but also relatively quick to go out of tune (especially when strung with gut strings), so they should tune to the more stable wind instruments. The oboe was one of the first wind instruments to be regularly added to the orchestra (in the Baroque period), and, for whatever reason, it is now used as the pitch standard (there's another good question). Oboes can't hit G3, therefore, we have the following set of constraints:

• Open string on violin: G3, D4, A4, E5
• Also an open string on viola & cello(8vb): G3, D4, A4 (no high E string)
• Also available on the oboe: D4, A4 (no low G)
• In a "comfortable" range on the oboe: A4(*)

(*) I am not an oboist, but I'm sort of assuming here that, at least on early instruments, the D4, which was the second-to-lowest note on the oboe, might have been a bit harsh sounding. I found a quote from Berlioz' Treatise on Orchestration which agrees with this notion: "The lower notes of the oboe, which sound ugly when exposed, may be suitable in certain harmonies of an eerie and sorrowful character..."

At any rate, I think the answer to your question will lie in discovering why the oboe is used as the reference pitch. Presumably, at least in the early Baroque, it would have been the continuo harpsichord (or organ) providing this reference, so maybe this shift coincided with the disappearance of continuo in the Classical era?

Some additional historical information that may be relevant:

In the early 6th century, when Boethius lists all the note names by letter, he starts (unsurprisingly!) with A as the lowest pitch. This presumably set a precedent for using A as a reference pitch.

In 1711, British trumpeter John Shore invented the tuning fork which allowed accurate tuning to a reference pitch. He even gave one to Handel, with a pitch of C=512Hz, corresponding to your scientific pitch.

In 1834, Johann Heinrich Scheibler, a silk manufacturer and acoustics researcher, invented a "tonometer" for accurately measuring pitches, based on an array of fifty-two tuning forks, spanning a range of pitches fro A3 to A4. Why did he choose A? I don't know! But this device allowed him to study a range of tunings in use at the time. He describes his tonometer in detail in Der Physikalische Und Musikalische Tonmesser, which is apparently available on amazon, if you fancy original sources and can read German.

Based on his studies, he recommended A4=440 to the Congress of Physicists in Stuttgart in 1834, which they accepted. The Streicher piano company also adopted this standard, manufacturing pianos with "440" stamped on the label. This wasn't the first attempt at standardized pitch, but due to Scheibler's tonometer, it was likely the most accurately measured standard up to that point. Nor would it be the last word in tuning; the French government passed a law on Feb. 16, 1859 requiring A=435, or "Diapason Normal" which would become widely adopted internationally.

For more reading:

• http://www.dolmetsch.com/musictheory27.htm (contains a chart of various pitch references throughout time, including Stuttgart's decision)

• http://drjazz.ca/musicians/pitchhistory.html (contains more information on Scheibler, and the history of tuning forks and A=440)

Answer 2

I think there are two questions here:

1. Why A?
2. Why A=440?

The first is reasonably answered - to tune a string instrument with no frets, the tuning note needs to be that of an open string, which limits it to G, D, A or E (violin). It is not suprising that A became the standard.

The A=440 question is far less easy to answer. I play early music (mainly recorders), and to cover all early music I would need a set of recorders at renaissance pitch (A=415), a set at baroque pitch (A=440) and a set at French Baroque pitch (A=466). Considering that at a minimum a set is 4 wooden instruments, the outlay is not insignificant.

Evidently the standard pitch of orchestras has been creeping upwards; A=446 is not unheard of. In the 1960s, brass bands were pitched about a quarter tone sharper than A=440 (as well as most instruments being Bb, so 3/4 of a tone below concert pitch). Most bands decided to lower their instruments to (B flat) concert pitch by adding extra tubing, but this ruined the tone of many good instruments. But I think all modern brass instruments are pitched at (B flat) concert pitch.

So why A=440?? I don't think there is a definitive answer.

Answer 3

I have played for 20 years and have been singing a lot...

I have come to the conclusion that 440hz is not good for singing at the top of your range... That is why the diapason standard was set at 435Hz back in 1859. Orchesters/concert halls wanted to go higher to create more brightness and cut (loudness) but limited the singers ability to get a great sounding high belt.. A lot of strain happens from 440Hz and above if you sing within your passaggio..

430Hz to 435Hz seems to be the best range for singing.. 430Hz is dark and chesty,, 435Hz has just the correct amount of mix for rock and pop without messing up the passaggio...

I am fairly deep baritone and the E4 note has always been tough at 440Hz.. needs a shift of register.. At 432Hz the E4 note can be sung naturally without changing register before the next note (F4)..

Why we never qustioned the 440Hz standard is beyond me... yes orchesters sound brighter and more exited but 432-434Hz is so much smoother and grandious..
The high connected headtone C5 of a tenor sounds better below 436Hz than up at 440Hz.. Even Pavarotti will have orchesters tuned around 440-442Hz down to 438Hz,, He would probable prefer lower like the Diapason normal (435Hz) but the orchesters instruments can't calibrate much lower as they are made for concert pitch (either 440Hz or 442Hz)..