The almost unknown manuscript RC 4 from the Silesian Museum in Opava was rediscovered by Jan Ciglbauer in 2011. A codicological analysis conducted by Ciglbauer and Gancarczyk in April 2017 revealed that RC 4 is one of the most important early sources of compositions by Petrus Wilhelmi de Grudencz.
The study gives a short glimpse of the musical contents and questions that arise as a result of the find.