A ligand may only be compatible with one of the two receptor parts, while the other part remains incompatible with the ligand.
To represent a partially compatible binding, we used a “perfect 4th” interval (simply 4 notes apart instead of 5, as used previously) to represent the cell receptor. The two tones are B-flat and E-flat. There are two examples of partially compatible bindings. First, we inserted a D between the tones- this is consonant with one of the two receptor notes (the B-flat, producing a major 3rd) and dissonant with the other (the E-flat, producing a minor 2nd).