Octave species various available intervals could be combined in any order, even restricting species to just the diatonic genus would result in twelve ways of dividing the octave (and his 17th-century editor, Marcus Meibom, pointed out that the actual number is 21), but "only seven species or forms are melodic and symphonic" . Those octave species that cannot be mapped onto the system are therefore rejected . In chant theory beginning in the 9th century, the "New Exposition" of the composite treatise called "Alia musica" developed an eightfold modal system from the seven diatonic octave species of ancient Greek theory, transmitted to
Short octave "C/E", meaning that the lowest note is a C, played on a key that normally would sound E. A second type of short octave used the keys to play the G major scale Here, the exotic bass notes C and D are sacrificed to obtain the more essential A and B. The notation for the pitch range of such an instrument is "G/B". The following diagram illustrates this kind of short octave: In stringed instruments like the harpsichord, the short octave system created a defect: the strings which were tuned to mismatch their keyboard notes were in general too short