A440 (pitch standard)

[2] Johann Heinrich Scheibler recommended A440 as a standard in 1834 after inventing the "tonometer" to measure pitch,[3] and it was approved by the Society of German Natural Scientists and Physicians at a meeting in Stuttgart the same year.

[5] In 1937 Sir James Swinburne, an electrical engineer and avid amateur musician, delivered a lecture to the Royal Musical Association on "The Ideal Scale," discussing the possibility of tuning a scale to pure ratios and adjusting these ratios to maintain consonance across different keys.

The following year, Swinburne represented the Musical Association at a preliminary conference to determine the British stance on concert pitch.

British piano tuners had adopted A439 as the standard in 1899, but Swinburne pointed out that 439 was a prime number, whereas 440 could be more easily factored and electronically synthesized.

In May of 1939, delegates from France, Germany, Holland, Italy, and England convened at Broadcasting House in London, the headquarters of the BBC, to address the issue of concert pitch.