Carl de Nys was born in Eupen, a small Belgian city in the northern part of the hilly Eifel and Ardennes area, next to the German border.
He was ordained as a priest in 1941 after studying in Verviers (near Liège in Belgium), and in Saint Dié and Nancy in French Lorraine. He chose to remain in France because he disliked the fact that the Belgian church concordant (ruling the priests' statute) would have made him a state employee. His career as a literature and philology teacher in Epinal was, however, very short. Instead, he was authorized by the Church's hierarchy to turn his attention exclusively to music and musicology.
According to witnesses, not only was he an excellent researcher and an enthusiastic historian and archeologist, (he was fascinated by each composer's personality and biography); but he was also blessed to an astonishing extent with a rare talent. He could mentally reconstruct the most complex musical composition by simply glancing through the score. This allowed him to identify the most promising pieces in the same way that you read your newspaper!
Carl de Nys revelled in religious music. He was also particularly fond of certain composers such as Mozart, M.A. Charpentier, W.F. Bach, and J. Haydn. Indeed, he took an active role in the progressive rediscovery of their work and wrote huge quantities about them. In addition, his eclecticism in musical matters allowed him the time to research many other composers all over Europe, some of them quite profane. It is remarkable that he was instrumental in the rediscovery of composers and great works not only in Germany or France; but also in Spain, Belgium, Scandinavia, and Bohemia. Despite his predilection for the 18th century, his research covered the entire span from Early Renaisssance to contemporary works.
He rejoined André Charlin in 1959 and remained his artistic director until Charlin's CECE ceased operations. This congenial duo of golden-eared music perfectionists, who could discern the slightest tone deviation in an orchestral performance, could have turned away conductors and artists. This was not the case. Instead, the artists gained motivation from the fact that their performance would be preserved in an optimum recording; as exemplified by their long association with Helmuth Müller-Brühl and his Kölner Kammerorchester, the Angelicum Orchestra in Milan, or Montserrat's Escolonia.
Carl de Nys was a meticulous researcher who was eager to make his discoveries available to the public. Together with H. Unnewehr and Prof. Overath in Dusseldorf and Cologne, he initiated Schwann's venture into music. With Maitre Jeghers in Liège, he founded Musique en Wallonie. He worked with publishers and orchestras in Prague, Italy and Spain; and on some occasions, when André Charlin was unavailable for a recording, he would work as a recording engineer himself. The resultant recordings document an undeniable technical ability.
Above all, however, he remained a teacher; as demonstrated by the volume of books he wrote about religious music, his countless articles about composers, and his strong involvement in broadcasting. In 1961, together with pianist Hélène Salomé and up in the cold highlands of Haute-Loire, he created the Centre Culturel de Valprivas; subsequently developing it into a shrine of musical sharing and learning. As luck would have it, soon after that, an old derelict mansion a few miles away was cleaned up and one of its old wooden cabinets reopened for possibly the first time in centuries. It was found to be full of notes. This is how Onslow was rediscovered. The very French gentleman-farmer with an English name, who was a contemporary of Beethoven, would become a further favourite of Carl de Nys.
It should be noted that Carl de Nys, as one of the greatest musicologists of this century, was not particularly appreciative of those excessively "historicising" interpretations which favour antique (yet harsh-sounding) instruments and a disturbingly slow tempo.
He may have thought that both music and history were better served by the rediscovery of deliciously intriguing contrasts; as exemplified by Tapray's Symphonie Concertante, with it's strange combination of piano and cembalo as solo instruments.