The location of a sound in the tonal scale, depending on the speed of vibrations from the source of the sound, fast ones producing a high pitch and slow ones a low. The rate of vibration per second is the note's ‘frequency’. By int. agreement of 1939, renewed and extended in 1960, the present‐day standard of ‘concert‐pitch’ to which instr. are tuned is that in which the A directly above middle C has 440 (double) vibrations per second (440 Hz), which makes middle C 261.6 Hz. This replaced the standard of 435 (diapason normal) fixed in Paris in 1859 and confirmed in Vienna in 1885. Before then, a variety of pitches existed. In Eng. in the 16th cent., domestic kbd. pitch was about 3 semitones lower than today's pitch and the church mus. pitch over 2 semitones higher. Between 1700 and 1850, the note A varied between 415 and 429. Pitch can now be measured electronically, but still the most common way is by a tuning‐fork. See A.