on the modern keyboard, the white keys are considered the diatonic notes, and scales (a series of notes in order from low to high or high to low) that can be made using only those whole-steps and half-steps are considered diatonic scales. In the Middle Ages, the church modes were based on diatonic scales.
In music theory, a diatonic scale (from the Greek Î´Î¹Î±Ï„Î¿Î½Î¹ÎºÎ¿Ï‚, meaning "[progressing] through tones", also known as the heptatonia prima and set form 7-35) is a seven-note musical scale comprising five whole-tone and two half-tone steps, in which the half tones are maximally separated. Thus between two half-tone steps there are either two or three whole tones, with the pattern repeating at the octave. The term diatonic originally referred to the diatonic genus, one of the three genera of the ancient Greeks.