Technique and precision
It must be said that in order to achieve a refined tuning, the ear and the mind must be trained to hear the harmony between notes and, therefore, reach the desired result.
It is a very complex technique which delicately combines the correct use of the wrench and a deep study of music.
In practice, tuning a piano consists in adjusting the tension of the strings so they sound at the correct frequency. The strings are adjusted by turning the pins with a special wrench. It takes a lot of practice and experience to do this job properly, as tuning involves adjusting the tension of every string in the piano. When the tension of the strings is altered, so is the pressure these apply on the soundboard, which, in turn, changes in shape due to these pressure fluctuations. This means that in order to achieve a stable tuning result, a comprehensive understanding of the behaviour of the instrument is required.
In musical terms, to tune means to build the musical scale by proportionally aligning its intervals. In the case of our Western musical scale of 12 notes, we use the “equal temperament” system, in which the distance between each semitone of an octave is exactly the same. This is the modern temperament.
The modern temperament is the theoretical basis of fixed tuning instruments’ tuning, as is the case of the piano. Temperament is the criteria used to solve the conflict that arises when trying to maintain the acoustic purity of every interval within the octave. It is acoustically impossible for each interval in each tonality to be pure. This derives from the actual definition of each musical interval.
Temperament has always been object of study and has also been the cause of protracted controversy. The temperament used worldwide nowadays to tune keyboard instruments (equal temperament) has been known since Ancient Greece times but has not been fully accepted until the end of the 19th century. This is because our temperament allows us to use every tonality without giving tuning priority to any of them, but at the same time to decrease the different “colours” that some of the old temperaments gave to each tonality. The criteria of the modern temperament is to abandon acoustic diversity and the different “personalities” the tonalities received with the old temperaments, in favour of the tonal universality needed for the praxis of contemporary music.