My custom Arduino wiitar adaptor. I used an Arduino pro micro, a classic controller extension cable, and a 5v to 3.3v stepdown chip to convert the wii guitar to a USB joystick,
raphnet. - Classic controller to USB adapter - V2
Genuine WII U Guitar Hero LIVE Guitar USB DONGLE wireless receiver adapter - Walmart.com
my favorite main guitar for clone hero (yes, it's a wii guitar) also i got this at goodwill for $3 - YouTube