With any of these designs[9], the chromatic layout is ideal for bilinear notation, with the added benefit that one system of note-heads will correspond to the bottom (and third) row of keys, while the other system of note-heads corresponds to the second row of keys:

When the instrument is transposed upwards by a semitone, the note-head types are reversed[10]:

The solution for the keyboard then is almost identical to the solution for notation. In fact, the positions of C, D, and E on the traditional keyboard and notation system are the same on both the (default) bilinear chromatic keyboard and in bilinear notation[11].