Chromaticism refers to combining pitches in a diatonic (major or minor) scale with pitches in the chromatic scale. For example, the ascending C major scale is as follows:

C-D-E-F-G-A-B-C

The equivalent chromatic scale is:

C-D-D#-E-F-F#-G-G#-A-A#-B-C

Chromaticism has been around for several hundred years – it was even used by Bach – and can be used to create a range of different harmonies and emotions that cannot be conveyed with a simple major or minor scale.