It’s responsible for reading the state of five 3D printed piano keys: three white, two black. It’s nowhere near a full octave, but for a doorbell, it’s enough.

The three white notes surrounding the two black keys are C, D, and E, and the four white notes surrounding the three black keys are F, G, A and B. So, if you count eight keys right from Middle C (or, ...

A man playing a piano built to the DS5.5 standard, with narrower keys than a conventional piano, plays an octave with a relaxed right hand and reaches a flat-eleventh chord with his left hand.

The accessory houses 15 white and 10 black piano keys, obviously setup in their normal pairings. Above the row of keys is a header bar containing volume options, octave switches and the iRig logo.

If you want to play different octaves, proximity sensors let you swipe left and right to move up and down the keyboard. If you prefer having more keys, you can add another Keys unit to either side.