Which Italian musical direction means to play softly?

A muon decays into two neutrinos and one of which particles? A murder suspect named Injun Joe appears in which Mark Twain novel? A museum in Springer, New Mexico, bears the name of which Old West trail that opened in 1821? A museum on Seattle's Main Street is named for which Klondike event of the 1890s that made the city a boomtown? What musical instrument is "das Klavier" in German? What type of musical decoration often hangs above a baby's crib? Which French composer wrote the 1859 opera "Faust"? Which musician and poet of Greek myth married Eurydice?