Which instrument has black and white keys?

The piano, whose 88 keys cover a little over seven octaves - about the full range in which the ear reliably hears a note as a note rather than a rumble or a click. Bartolomeo Cristofori built the first around 1700, and the invention was the action rather than the keyboard: a mechanism that throws a hammer at the string and immediately lets it fall away, so how hard you press decides how loud the note is.

That was the thing the harpsichord could not do. A harpsichord plucks, and plucks the same way however you hit the key, so dynamics have to be faked by changing register. Cristofori called his instrument the gravicembalo col piano e forte - the harpsichord with soft and loud - and the name shortened to pianoforte and then to piano.

The black and white arrangement is not decorative. The pattern of two and three black keys is a navigation aid, letting a player find a position by feel without looking, and it encodes the seven-note diatonic scale with five additions. Early instruments often had the colours reversed, with dark naturals and pale sharps, and the modern arrangement settled mostly because ivory was expensive and used for the keys that get touched most.