I was reading the Idiot's Guides: Music Theory (3rd edition), and I read:
The "standard" pitch today that most musicians tune to is the A above middle C, which equals 440 Hz; all the other notes are pitched in relation to this note. In earlier times and cultures, this note had other values—as low as 376 Hz in early eighteenth-centrury France, and as high as 560 Hz in early seventeenth-century Germany (referred to as North German church pitch).
The book doesn't really explain why today 440 Hz is considered the "standard pitch". Does playing a musical instrument tuned to 440 Hz offer any benefits over other frequencies?