Phonology of Voynichese

[geoffreycaveney]

The idea of an abjad could well be one of the most important aspects when considering Voynichese phonology. 
If the writing system is not an abjad, vowels and consonant should alternate; they should cumulative have something (very roughly) comparable with a 50-50 share of character occurrences (not types: vowels will have less types, with more occurrences per type). That is basically the principle underlying both Sukhotin's algorithm and Hudson's OCP software (and possibly 2-states HMM as well).
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On the other hand, if the script is an abjad, it might be as you say. I don't know much about abjads, but if vowels can sometimes be totally absent, then (if Voynichese is such a case) y would obviously represent a consonant.
Abjads are a subject I would like to investigate more. For what is worth, the fact that Sukhotin's algorithm results in a higher Consonant-Vowel alternation rate for the VMS than for the comparison languages I have checked (German, Italian, Latin, English) suggests that Voynichese does represent vowels.

There is one more possibility that needs to be considered as well - that of an "impure abjad":

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I quote:
"Impure abjads have characters for some vowels, optional vowel diacritics, or both. The term pure abjad refers to scripts entirely lacking in vowel indicators.You are not allowed to view links. Register or Login to view. However, most modern abjads, such as You are not allowed to view links. Register or Login to view., You are not allowed to view links. Register or Login to view., You are not allowed to view links. Register or Login to view., and You are not allowed to view links. Register or Login to view., are "impure" abjads – that is, they also contain symbols for some of the vowel phonemes, although the said non-diacritic vowel letters are also used to write certain consonants, particularly You are not allowed to view links. Register or Login to view. that sound similar to long vowels. A "pure" abjad is exemplified (perhaps) by very early forms of ancient You are not allowed to view links. Register or Login to view., though at some point (at least by the 9th century BC) it and most of the contemporary Semitic abjads had begun to overload a few of the consonant symbols with a secondary function as vowel markers, called You are not allowed to view links. Register or Login to view..You are not allowed to view links. Register or Login to view. This practice was at first rare and limited in scope but became increasingly common and more developed in later times."

Thus, the choices do not have to be limited to the two options "all vowels represented" or "no vowels represented". In impure abjads, we have some of the vowels represented, but in a less consistent manner than full alphabets do.

Note in particular the statement in the quote about how "vowel letters are also used to write certain consonants, particularly approximants that sound similar to long vowels". Also note the statement about how "Semitic abjads had begun to overload a few of the consonant symbols with a secondary function as vowel markers". This concept of overloading symbols with multiple functions, representing multiple sounds and types of sounds, may be relevant to the Voynich MS as well.

Geoffrey