Modern Pianos are tuned to equal temperament at A440. Are there other prominent alternate tunings used in art music or popular music? I'm accepting that historical reproductions will tune the A to 430 or something, but I'm thinking different tuning models?
UPDATE: Thanks for the answers! I guess more what I'm thinking of is anyone anywhere experimenting with different ways to tune the instrument. I saw a video of a specially made piano where EVERY key is middle C! what other experiments are going on?
There are two recent approaches to modern temperament design that have interested me:
One is Bill Bremmer's EBVT temperament, which has undergone some revisions in recent years. It started with a compromise between temperaments of the "victorian" style and equal temperament, to suit an aesthetic that favors variation in dissonance across the circle of fifths, but is still comfortable to the modern ear in the distant keys. More recently it has focused on the contribution of temperament design to beat cancellation. That is, focusing on beat rates of interval tests in isolation does not take into account the effect of temperament on beats in chords and larger combinations of intervals.
Another is the "pure twelfths" approach exemplified by the work of Bernhard Stopper, which also focuses on the beat cancellation idea, but comes at it from a mathematical approach.
If the question is concerning experimentation in temperament design, then historical temperaments don't really apply since those such as Werkmeister or meantone have accepted definitions which are not changing. People experiment with their applicability to certain situations like spinet scales or period performance, but they are not experiments with temperament design.