[GRiMe2D]

Actually Bach's Well Tempered Clavier IS a book written in a single set of tuning system that actually lost/forgotten. We still have discussions about how it's constructed. For more information google "Well Tempered Clavier interpretation"

You can listen to variations here: https://youtu.be/kRui9apjWAY?t=622

[tadfisher]

Neither lost nor forgotten! It's the basis for the "Thidell Formula 1" temperament [0], which is what produces those squiggly frets on expensive guitars. It also works well for multiple keys (at the expense of others), making it a compromise for a range of music rather than a single song.

0: https://www.guyguitars.com/truetemperament/eng/tt_techdetail...