Curiousity got the best of me. Had to find it for myself also. Answers.com has an massive and extensive explanation of tuning systems beginning with Pythagoras. I knew that, about the ancients' tuning. But I will go back and read the rest. Looks interesting and thorough. Don't know if it's enough for me to judge if it is enough info. Just telling anyone in case they want their piano tuned. My needs it badly.....wouldn't dream of tuning it myself.....

1) "The first Meantone tunings are described in late 16th century treatises by Francisco Salinas and Gioseffo Zarlino. Salinas (in De musica libra septum) describes three different mean tone temperaments: the 1/3 comma system, the 2/7 comma system, and the 1/4 comma system. He is the likely inventor of the 1/3 system, while he and Zarlino both wrote on the 2/7 system, apparently independently. Lodovico Fogliano mentions the 1/4 comma system, but offers no discussion of it. These formulations were often more theoretical than practical, as scientific methods to precisely determine the pitch of a string from its physical attributes were inadequate, and tuning had to be done by ear. For instance, to achieve the 1/4 comma system Salinas recommends tuning the 5ths as low as the ear will allow. Although Meantone is best known as a tuning environment associated with earlier music of the Renaissance and Baroque, there is evidence of continuous usage of meantone as a keyboard temperament well into the middle of the 19th century. Meantone temperament has had considerable revival for early music performance in the late 20th century and in newly-composed works specifically demanding meantone by composers including György Ligeti and Douglas Leedy." Source and further information: http://en.wikipedia.org/wiki/Meantone_temperament Further information: http://en.wikipedia.org/wiki/Equal_temperament http://en.wikipedia.org/wiki/Piano_tuning http://www.amarilli.co.uk/piano/theory/idisc02.asp 2) "During much of the 20th century it was assumed that Bach wanted equal temperament, which had been described by theorists and musicians for at least a century before Bach's birth. However, research has continued into various unequal systems contemporary with Bach's career. Accounts of Bach's own tuning practice are few and inexact. The two most cited sources are Forkel, Bach's first biographer, and Friedrich Wilhelm Marpurg, who received information from Bach's sons and pupils, and Johann Kirnberger, one of those pupils. Forkel reports that Bach tuned his own harpsichords and clavichords and found other people's tunings unsatisfactory; his own allowed him to play in all keys and to modulate into distant keys almost without the listeners noticing it. Marpurg and Kirnberger, in the course of a heated debate, appear to agree that Bach required all the major thirds to be sharper than pure—which is in any case virtually a prerequisite for any temperament to be good in all keys. Johann Georg Neidhardt, writing in 1724 and 1732, described a range of unequal and near-equal temperaments (as well as equal temperament itself), which can be successfully used to perform some of Bach's music, and were later praised by some of Bach's pupils and associates. J.S. Bach's son Carl Philipp Emanuel Bach himself published a rather vague tuning method which was close to but still not equal temperament: having only "most of" the fifths tempered, without saying which ones or by how much." Source and further information: http://en.wikipedia.org/wiki/Well-Tempered_Clavier