Figure an Arduino most matches the "Other" category. To be specific, it isn't an Arduino brand, it is a DigiSpark, but the trouble isn't with the device itself. The problem is with a buzzer. I got ...

Each buzzer consists of an Arduino Pro Mini 3.3 V, a nRF24L01, and of course a big pushbutton on the top. ... So user can stick his finger on the RF tuned circuit?

The Casio SK-1 keyboard is fairly well-known in the “circuit bending” scene, where its simple internals lend themselves to modifications and tweaks to adjust the device’s output i… ...