Pitch (music) - Concert Pitch

Concert Pitch

Concert pitch is the pitch reference to which a group of musical instruments are tuned for a performance. Concert pitch may vary from ensemble to ensemble, and has varied widely over musical history.

The A above middle C is usually set at 440 Hz (often written as "A = 440 Hz" or sometimes "A440"), although other frequencies are also often used, such as 442 Hz. Historically, this A has been tuned to a variety of higher and lower pitches. For example, Michael Praetorius proposed a standard of 465 Hz in the early 17th century.

The transposing instruments in an orchestra will conventionally have their parts transposed into different keys from the other instruments (and even from each other). As a result, musicians need a way to refer to a particular pitch in an unambiguous manner when talking to different sections of the orchestra.

For example, the most common type of clarinet or trumpet, when playing a note written in their part as C, will sound a pitch that would be called B♭ on a non-transposing instrument like a piano. If you wanted to refer to that pitch unambiguously, you would call it "concert B♭", meaning "the pitch that someone playing a non-transposing instrument like a piano would call B♭".