There are many materials available from which you can make miniatures, but one of the most versatile of these is polymer clay. Polymer clay is convenient in that it bakes hard in the oven and is easy to paint. For miniatures, polymer clay is especially useful for making odd or unusual shapes that you can't easily find or make from other materials. When making a miniature phonograph, you can mold polymer clay to form the curved horn that projects the sound.
Trace a circle onto the cardboard with the compass and cut it out.
Cut a slit in the cardboard circle from the edge to the center, and then roll it into a cone. Hold it to the rest of the phonograph to make sure that it is a suitable size. Staple the cone closed. This is a form for your clay.
Warm up a piece of polymer clay by rolling it in your hands, and then roll it into a flat sheet using a plastic clay roller.
Cut a circle from the polymer clay sheet and wrap it around the cardboard cone, cutting away the excess and smoothing out the seams with your fingers.
Roll a small cone from clay and attach it to the small end of the big clay cone, smoothing out the seams with your fingers. Twist the end to fit onto the phonograph. Phonograph horns can be many shapes and often have a decorative look, so be creative with the end of the horn.
Remove the cardboard form and press the edges of the horn outwards with your fingers, creating a flare at the end.
Bake in an oven according to the instructions on the clay. Time and temperatures will vary depending upon the brand.
Paint the horn with metallic craft paint.
The clay may be very soft when you try to remove the cardboard, which will cause the shape to collapse. If you leave it alone for a day or two, the cardboard will absorb extra plasticizers in the clay and stiffen it. For a brighter, more metallic look, use a metallic wax instead of paint.