ORGANISTRUM IN SANTIAGO DE COMPOSTELA: SYMPHONIA COELESTIS

The famous Portico of the Glory in the Cathedral of Santiago de Compostela (Galicia), dedicated to St. James, recently also examined in an interesting archaeoastronomical perspective (Vilas Estevéz and Gonzalez–Garcia, 2016), has been built following an iconographic project inspired by St. John’s book of Apocalypse (Moralejo, 1988). At the top of the main arch, in the middle of the 24 venerable men’s row around Christ’s throne, there is a peculiar musical instrument – equipped with a wheel – played by two of them. The particular position, the extremely accurate details and the peculiarity of the instrument underline the importance of an object whose origins, symbolism and actual musical role (Lopez–Calo, 1988) have never been completely explained. The most intriguing features are: a) 12 interval division of the octave; b) wheel used to produce sound; c) general shape and decorations. In this article we introduce a possible interpretation of Symphonia (the so–called Organistrum) as a sampler of cosmological and astronomical knowledge typical of European culture from the ninth to the twelth century (Eastwood, 1987; McCluskey, 1998). Close relationship between astronomy and music in platonic–pythagorean doctrines is confirmed through detailed analysis of astronomical texts in manuscripts copied in Benedictine scriptoria from Carolingian Renaissance onwards (Eastwood, 2007). Beyond general reference to Plato’s Timaeus, through Macrobius and Calcidius commentaries (Martello, 2011), the main suggestions for our study come from interesting diagrams (Eastwood and Grasshoff, 2004) found in these manuscripts (e.g.: clm 14436, f.61r, Munich Bayerische Staatsbibliothek).