It looks and plays like a piano, but it sounds like a string quartet — and it took 500 years before anyone built it. Leonardo da Vinci’s flight of fancy in designing a hammerless piano, called a “viola organista,†has come to life half a millenium after da Vinci designed it, thanks to a Polish concert pianist and musical engineer. It couldn’t have sounded any better in da Vinci’s head (via Brad Thor and Dan Gainor): A bizarre instrument combining a piano and cello has finally been played to an audience more than 500 years after it was dreamt up...