The 1920s saw a movement of modern mass production methods in the toy industry.  Tin toys, pressed metal and cast-iron toys, wooden and paper toys were now able to be produced cheaply.  Small musical toys made in the shape of musical instruments became very popular, especially the free-reed musical toys that produce sound as air flows past a vibrating reed or comb of reeds in a frame (much like a harmonica or accordion).  Then in 1927 polystyrene was invented.  It was a tough, durable kind of plastic that was ideally suited to toy design, ushering in a new world of musical toy development for the following decades.