28. The method of claim 27 , wherein both the first and the second key planes include a set of medial phonetic symbols of the phonetic alphabet.
28. The method of claim 27 , wherein both the first and the second key planes include a set of medial phonetic symbols of the phonetic alphabet. 31. The method of claim 28 , further comprising: while the second key plane is being presented, receiving user input adding a tone mark to a symbol input sequence following a medial or a final phonetic symbol; and upon receiving the user input, presenting the first key plane of the virtual keyboard in place of the second key plane.