Count Unico Wilhelm van Wassenaer (born November 2, 1692, Delden - died November 9, 1766, The Hague) was a Dutch diplomat and composer.His most important surviving compositions are the Concerti Armonici
, which until recently have been falsely attributed to the Italian composer Giovanni Pergolesi (1710-1736).\
Unico Willem Van Wassenaer was born into a distinguished family of wealth, power and accomplishment. He studied law and other courses in Leiden and in 1723 married Dodnea Lucia van Goslinga, who gave him three children. Van Wassenaer occupied high diplomatic, military and commercial posts. It is known that he was respected not only as a diplomat but also as a musician.Between 1725 and 1740 he wrote the Concerti Armonici, but being a nobleman he did not want to publish them in his own name (or because he doubted his ability as a composer). The concertos were published in 1740 by the Italian violin player Carlo Ricciotti (1681-1756), to whom the concertos would be attributed at first. Van Wassenaer has therefore been called "the mystery composer."The Polish composer FranÃ§ois Lessel (1780-1835) asserted incorrectly that the concertos were written by Pergolesi. Since the style of the concertos is Italian, laid out in typical Roman fashion with four parts for violin and consisting of four parts instead of the Venetian three, they are comparable to works by Pietro Locatelli.
However, in 1979-80 a manuscript of the six concerti was found in the archives of Twickel Castle (the castle where Van Wassenaer was born), labelled 'Concerti Armonici'. Although the handwriting was not by Van Wassenaer, the manuscript did have an introduction in his hand, reading: "Partition de mes concerts gravez par le Sr. Ricciotti". Because of the research done by the Dutch musicologist Albert Dunning, there can be no doubt that the concerti were written by Van Wassenaer.
Apart from that, three sonatas for recorder and continuo have been discovered in the early 1990s. (Wikipedia)