Semiology, derived from ' Semeion' (Gr. sign) is a relatively new branch of Gregorian Chant research. Semiology refers specifically to the study of the neumes as found in the earliest fully notated manuscripts of so called Gregorian Chant that were written as early as ca. 930. The term was coined by Dom Eugene Cardine, monk of Solesmes (1905-1988), who worked out a coherent analysis of the various neumes and their musical significances. As such, 'semiology' is to be understood as 'study of signs'. Cardine was able to show the internal logic and coherence in the neumatic notation with regard to a proper articulation of the verbal-melodic line. Cardines' insights have been furthered by his students, who have managed to create a shift to a greater rhythmic diversity in performances of Gregorian Chant.
'Semiologie Gregorienne' was published by Solesmes in 1970. In the book Cardine presents an enlightening comprehensive table of neumes as were used by the school of Skt. Gallen. Vertical, from top to bottom, in the first column, he starts off with neumes representing a single note, then two-, three- and four-note groups and many compound neumes and ornamental neumes. Horizontally Cardine enters all existing varieties of the main neume. A simple glance over the table will eradicate any pre-conceived ideas that this is in someway 'primitive'. Actually, in respect to its function and purpose the Sankt Gallen notation is very sophisticated. Both the text and melody were deeply implanted in the minds of the experienced singers as long as memory did not mix up. So not only do text and neumatic notation together present an effective integral mnemonic technique, it does more than that: it gives a specific shape and contour to the calligraphy of the verbal-melodic lines. Our modern, very exact notation compares like type-writing to calligraphy. In calligraphy, there is an organic rhythm to the movement of the pen on the paper and many connections beween letters can be made in various ways, ornaments can be integrated into the line which in type-writing can not be done. Also, in the latter there is a very even spacing, as in modern notation. Even square notation, which utilizes many ligatures, can do no full justice to the detailed information found in the early neumatic manuscripts. As Cardine points out, natural speech-rhythms provide a rhythmic basis for declamation, in which at least five syllabic durations can be distilled, as in medium,long/short, longer/shorter. Compare 'filii tui' with 'non confundentur', the first a quick succession of shorts, the second the opposite. This difference in syllabic 'space' should be respected in texted parts, whereas in longer melodies sung on one protracted vowel the neumes indicate the melo-rhythm in a precise and very coherent way.
Cardine's work was recognized and supported by (Vatican commissions and led to the publication of the Graduale Triplex in 1979, which was based on Cardine's personal Roman Gradual in which over the years he had copied many neumes from Skt. Gallen school manuscripts. Two students of Cardine, Rupert Fischer and M.C. Billecocq undertook the strenuous task to manually copy the neumes of two schools of generally concordant rhythmic manuscripts (Sankt Gallen + Einsiedeln and Laon/Metz) into the new type-set Roman Gradual of 1974. In hindsight, the Graduale Triplex proved a great stimulus for self-study as it made important material available in a handy book. A giant step forward was made with its publication, the momentum of which has created a demand for yet another Gradual as the 1974 contains many incidental or structural melodic errors. The relative small but growing number of choirs or small groups that perform Gregorian Chant according to these recent developments are thus said to follow the 'semiological approach', which is the Gregorian Way of being HIP (Historically Informed Performance). Though semiology has given a huge impuls to research and performance, many other parameters need to be addressed to credit full HIP-ness.
Students of Cardine, who also held a professorate at the Pontifical Institute in Rome, next to the two already mentioned, include Marie-Noel Colette, Luigi Augustoni, Godehard Joppich to name a few that are noted experts in their own right.