Adding to the pile, here is a photo of Wynton Marsalis trying a 4-valve picc. Notice (barely visible at this angle) that his left pinky is holding down the 4th valve.
Dave Werden (ASCAP) Euphonium Soloist, U.S. Coast Guard Band, retired Adams Artist (Adams E3)
Alliance Mouthpiece (DC3) YouTube: dwerden Facebook: davewerden Twitter: davewerden Instagram: davewerdeneuphonium