If you are not a musicologist, you might be wondering what A415 is as you read this blog. It's a little complicated, but we promise it won't hertz. Jeff Phillips, our Artistic Administrator, explains:
Historically there were many different pitches to which groups of musicians tuned, based on local tradition or, in the Baroque era, to the pitch the local organ was set as it was impractical to tune otherwise. This pitch varied from about A=380 Hz to as high as A=480 Hz, based on surviving examples. In the nineteenth century it became clear that settling on a standard pitch across Europe would be a good idea--France even passed a law setting A=435 in 1859--but the standard "concert pitch" was finally set to A=440 only in the mid-1900s. While 440 is still the worldwide standard, among professional orchestras the pitch continued to rise to accommodate larger concert halls, with most settling on 442 or 445; a higher pitch is perceived as brighter, and therefore louder, by the listener.
Since period-instrument makers and musicians needed a pitch standard on which to settle, most period-instrument ensembles, Philharmonia included, use A=415 Hz as their pitch standard for Baroque music, since it's almost exactly a half-step lower than concert pitch. Harpsichords and organs are built with the ability to shift back and forth between pitches easily, strings sound a bit warmer, and singers are generally happier to be able to sing their high notes without strain.
The image is above is a page of George Frideric Handel’s autograph draft score of Messiah, 1741 (The Granger Collection, New York).