A key is a hierarchy of tones (scale), which is based on a basic tone (tonic). Examples for keys: C-minor: minor-scale with the basic tone C (comprising the tones C, D, Es F, G, As, B, C), Fis-major: major-scale with the basic tone Fis (comprising the tones Fis, Gis, Ais, H, Cis, Dis, Eis, Fis).