C Chromatic
C · D♭ · D · E♭ · E · F · G♭ · G · A♭ · A · B♭ · B
All twelve notes, each a semitone apart — C Chromatic isn't a key so much as the complete set of available pitches. Nobody improvises in it directly; its value is as a source of passing notes and chromatic approach tones that connect the notes of whatever scale you're actually playing. Used sparingly, it's what makes lines sound fluid.
Left-handed