Muffs, or handwarmers, went out of fashion long ago. I did have one made of fur when I was a kid . It was very cozy, though not very practical for a child who nevers sits still. Likewise, having a handwarmer that is shaped like a concertina may not seem like a very practical accessory, but it is an interesting way to keep your hands warm. So why wear an ordinary pair of mittens, when you could stuff your hands into a knitted squeezebox and hum a Zydeco tune?