Every musical pitch has its own standardized rate of vibration. However, that uniformity has not always existed. Beethoven, for example, would be shocked to hear his music played with today’s pitches.
Quick briefing on musical history
Actually, throughout most of music history, written notes did not stand for exact, or “absolute,” pitches. Written notes simply indicated relationships between each other. Performers would select a pitch level at the beginning of a composition and then perform the rest of the notes relative to that starting point.
Later, musicians tried to establish absolute pitches, but there was much disagreement and confusion. For example, during the baroque period (c. 1600 to c. 1750), different pitch levels were used depending on the purpose of the music: low pitch levels for church music (choir and organ), higher levels for domestic instrumental music, and even higher levels for brass music played by town musicians. However, the absolute pitch of these pitch levels varied with the time and place.
The next hundred years
For the next hundred years, even after the baroque gave way to the classical and early romantic periods, absolute pitch continued to vary. Finally, in 1859 the Paris Academy fixed the standard of pitch at A (above middle C) = 435 cycles (complete vibrations, or back-and-forth movements) per second. From that pitch, others were obtained by mathematical formulas. In 1885 that standard was confirmed under the term “international pitch” at a conference in Vienna, Austria. In 1939 another international conference, in London, England, raised the standard to A (above middle C) = 440 cycles per second, where it remains today.
Beethoven (1770-1827) lived during the period of variable absolute pitches. However, in his time and place, Austria, the standard instrumental pitch, though variable, was consistently about a semitone (half-tone, half step) below our modern standard. For example, a Mozart tuning fork dated 1780 was tuned at A (above middle C) = 422 cycles per second, approximately a semitone lower than today. Therefore, works of that period sounded about a semitone lower than they do when performed at the present standard of pitch.
Imagine going back to Beethoven’s time and listening to a performance of his famous Fifth Symphony in C minor. To our ears, Beethoven’s C would sound more like B. And if Beethoven could hear a modern performance, he would cringe listening to his symphony in what would probably sound to him like an out-of-tune C-sharp.
Source: Music Guides Hub