Today, most instruments are tuned to concert pitch, but there was no universal standard in early music. Before the 19th century, an A played by one instrument might have sounded a B on another; so every instrument in an orchestra needed to be aligned in pitch before they could play as an ensemble. One solution to this confusion was the transposing keyboard, which allowed a performer to quickly change the home key of their instrument.
Eventually, pitch became standardized through a series of laws:
- Continental Pitch (A = 435 Hz): 1859 France
- New Philharmonic Pitch (A = 439 Hz): 1896 England
- Concert Pitch (A = 440 Hz): 1939 & 1955, international
- 8-foot pitch (for keyboard instruments)