I'm trying to make a simple theremin project with the Elegoo Uno R3 following an online tutorial (link in comments), but there's an error of "redefinition of 'void setup()'", I'm pretty sure
Ultrasonic Theremin | Arduino Project Hub
Arduino Optical/Light Theremin – Make it Yourself! - Codrey Electronics
How to Make Arduino Theremin -Control Arduino With Proximity - Hackster.io