Another essay split into three to circumvent the post limit. Hope you find it interesting.
Part 1
While much has been written on the subject of equal temperament, most of these academic works have concentrated on the development of tempered tuning systems for the historic range of keyboard instruments. The influence of early fretted instruments has been neglected a little yet the early lutenists were probably the first musicians to encounter the seemingly insurmountable issues of tuning and temperament and were also some of the most important figures in the eventual development of a universal solution.
The difficulties presented in producing a system of tuning with a range of fixed pitch values had been known since the days of the Babylonian Empire however it was Pythagoras, drawing upon the works of the sophisticated Babylonian mathematicians who first presented us with a mathematical model of the chromatic scale. Pythagoras however was not a musician, but the leader of a monotheistic religious movement whose precepts would later come to influence a number of world religions including Buddhism, Sufi Islam and Christianity. What Pythagoras was investigating was not music but the science of harmonics which he believe held the key to understanding the nature of the universe and ultimately the mind of God. Pythagoras expressed the pitch value of a note in terms of divisions of its length, although it would be another two thousand years before anyone made an accurate connection between tension and pitch.
Greek music at the time of Pythagoras was centred around the major divisions of the octave, the diapason,the diatessaron and the diapente and was mostly played on wind instruments and multi-strung harp-like instruments such as the lyra and kithara, the latter of which bequeathed us the names for a host of instruments; zither, sitar, cittern, chitarrone, guitarra and ultimately, guitar.
Fretted instruments were virtually unknown at this time in Europe (although it is believed that they were in use in India and Persia), however by the time of the Crusades traders, pilgrims and crusaders were returning from Asia Minor with examples of an Arabic instrument called the al 'ud. The name means, literally, the wood and soon European makers were copying its design, Al'ud became Lute, from which we get the word luthier which originally meant lute maker but which we now apply to any guitar maker. Its original pronunciation was, incidentally, lutier, with a "t" sound for the "th", and it was as readily applied to lute players as it was to lute makers as the distinction between the two was often blurred.
The fact that we have a historical word for the maker of lutes (we do not have one for violin makers or harpsichord makers for example) is some indication of the level of respect reserved for this particular artisan.
A practice that had been in use for some time in Europe involved tying loops of gut string around the neck of a fretted instrument to provide a division point for the string and define the note. Primarily found on folk instruments such as the rebec and the Celtic crwth (spelled crouth and crowd in England and the origin of the name Crowther) these frets initially did little more than divide the string into the major intervals of the fifth and the fourth, or to use the Greek terms, diapente and diatessaron. By about the late mediaeval age however lutenists were quite adventurous and the requirements of full polyphony could only be accommodated by a full chromatic scale. Such a scale existed, courtesy of Pythagoras, but things were not that simple...
To be continued