Older readers may remember the Stylophone, a small battery powered electric organ using conductive PCB pads and a stylus to create notes. The simple multivibrators in those instruments made them monophonic, but here in 2021 we can do better than that! [Sjm4306] has gone the extra mile with a PCB organ, by making a capacitive-touch instrument that boasts four-note polyphony.
At its heart is an ATmega328p whose software sports four tone generators that each emerge on a different pin. These are summed using a set of 100 Ω resistors and fed to a tiny speaker. Power comes from a CR2032 lithium cell, and he notes that a higher voltage delivers more volume.
The full story is detailed in the video below the break, along with a bit of four-note polyphonic action. We’re guessing that this instrument would sound sensational when hooked up to a reverb unit.