Using easily-identified octaves, fifths, and thirds, seventeenth century musicologists devised common major and minor scales in a pattern of twelve half tones between each octave. This system accounted for a variety of factors, making it straightforward to play 'natural' scales and chords of fifths, thirds, and fourths. The challenge that arose with respect to keyboard instruments was when departures from those homogeneous scales and chords were desired.

 

This system was far from a forgone conclusion. There were virtually unlimited options presented to the musicologists of the fifteenth and sixteenth centuries. The Gregorian chants introduced and developed several modes, or simple scales. In addition, there are many more. Musical innovators thus introduced a concept of 'equal temperament' based on a twelve-note division of the octave.

     

One may ask . . . how many scales are there? The answer is in the hundreds. How then should one deal with such a subject, and how important are all these scales? The easy way out of the whole problem is for everyone to perform in equal temperament. However, musicians are very independent, and they will never do this. The important thing is to appreciate the differences that can exist between the frequencies of notes in various scales and to play accordingly with knowledge and sense, so that the timbre is not spoiled.    

 

Equal temperament results in that only one interval is 'perfect' (entirely in tune)--the octave. All other intervals in this system--referred to as a 'chromatic' system--are compromises in the physics of musical sound. Though we have been conditioned to accept this system as natural and pure, it was an unusual compromise when it was initially introduced.

 

The 20th-century ear has become accustomed to the errors introduced by the equally tempered scale, and in some cases the errors introduced are preferred to pure intervals. Serious problems exist when we have one player performing in a scale such as equal temperament and another playing in a different scale. This can easily happen when strings play in ensemble with piano or organ. Indeed, in performances, one can hear the string players reacting to the errors of the equally tempered scale and modifying their somewhat perfect intervals, which had previously seemed more natural.  

 

 

Andreas Werckmeister in his 1691 publication Musical Temperament promulgated equal temperament. Johann Sebastian Bach responded to this work in the composition of The Well-Tempered Clavier, a two volume keyboard work including forty-eight preludes and fugues in all of the major and minor keys represented by the concept of equal temperament. Acceptance of this concept--critical to the success of the fully integrated symphony--was not a foregone conclusion. Bach's work helped to establish this feature as a keyboard standard.

 

Mean-tone temperament was in general use in his day, meaning that different keyboard instruments would have half tones of different sizes. Friedrich Wilhelm Marpurg, a contemporary of Bach, wrote, "Three scales [with equal temperament] were made ugly in order to make one beautiful." Percy Scholes indicated:

     

It is not possible to tune any keyed instrument perfectly for more than one key; if you tune it correctly for key C, the moment you play in another key some of the notes will be out of tune. On the mean-tone temperament just a single key was perfect, but, by a compromise, a certain number of keys were made near enough perfect for the ear to tolerate them, the rest being outside the pale.

 

 

Equal temperament provided a basis not only for keyboard flexibility, it allowed for full modulation (merging from one key to another within the body of the music). Equal temperament also provided an example for the kind of compromise that would be necessary to integrate all of the instruments in the symphony.