are made of ebony and the black notes are covered with softer white bone. A few electric and electronic instruments from the 1960s and subsequent decades have also done this; Vox's electronic organs of the 1960s, Farfisa's FAST portable organs, Hohner's Clavinet L, one version of the Korg Poly-800 synthesizer and Roland's digital harpsichords.

Some 1960s electronic organs used reverse colors or gray sharps or naturals to indicate the lower part (or parts) of a single