I've made a launchpad with an arduino leonardo, and a stereo head mask to go along with the overall theme of "object head" characters.
-leather (I specifically used goatskin, which can be found at your local hobby lobby)
Launch pad materials
-4X M3 10mm Screws
Step 1: Making the Base
I used a small square of cardboard and nailed it into the bike helmet.
After that I secured the nails with some gorilla glue just to be extra safe so it doesn't move, rotate around.
For safety, make sure your helmet is thick enough that whatever length nails you buy doesn't poke through the other side.
Step 2: Building the "shell" of the Stereo Head
I used 1-2 inch foam blocks and glued them on with gorilla glue on the top of the cardboard- this is where the "top" of your mask will lie.
I measured from the top of the foam blocks to about a half inch below my chin. For me, I ended up with two measuresments of 9x13inch (front/back) and 13x14inch (sides) rectangles for my outer shell. However measurements will vary based on your head size.
After measurements, cut out the sides, and the top. I used tape to secure everything. I'd recommend something sturdy like duct tape.
Make sure you cut out a hole, in whatever shape or fashion you desire, so you have a place to see.
Step 3: Finishing the Shell of the Mask
I bought scraps of goat skin from hobby lobby.
I cut out pieces of craft foam the same size as the cardboard from earlier and wrapped the goat skin around the pieces, gluing them from the back size with gorilla glue.
Then I proceeded to place them on their respective sides. The goatskin added a nice sheen and retro feel to the mask, however, if you want your stereo head to look differently, feel free to use whatever you want for the outer shell.
I used other scraps of leather and foam to seal off the edges to give it an overall, complete finish.
Step 4: Launchpad
Step 5: Done!
And you should have a neat radio head mask and a launchpad you can make music with! A nice musical themed costume for you, perhaps.
As for making the launchpad mobile, it depends on your phone. I have a google pixel 2 and I had lots of trouble finding good apps in the store that worked well. Garageband was the one program that worked the best in my opinion, if you can get your hands on an iphone, or ipad.