2. In this chapter, you learned that some pathogens must attach to host cells to cause disease. To accomplish this, molecules on their surface (adhesins or ligands) recognize and attach to molecules (receptors or integrins) on the surface on certain host cells.
So a chromatic note, is any note you play that is not in the scale you are playing. They are also a great way to practice, especially if you are going through the pentatonic scale. Try adding one of these outside chromatic notes to your scale, and see how it sounds above the chord you are playing over.
Chroma, a measure of color purity in the Munsell color system. Chroma feature refers to the color of a musical pitch, which can be decomposed in into an octave-invariant value called chroma and a pitch height that indicates the octave the pitch is in.