The work of Alypius consists wholly, with the exception of a short introduction, of lists of the symbols used (both for voice and instrument) to denote all the sounds in the forty-five scales produced by taking each of the fifteen modes in the three genera (diatonic, chromatic, enharmonic). It treats, therefore, in fact, of only one (the fifth, namely) of the seven branches into which the subject is, as usual, divided in the introduction; and may possibly be merely a fragment of a larger work.
Alypius's work is focused solely on a single aspect of the broader topic of musical scales and modes, which are divided into seven branches. It is likely a fragment of a larger work.