[1] Wilhelmj was born in Usingen and was considered a child prodigy; when Henriette Sontag heard him in 1852 at seven years old, she said, "You will be the German Paganini".

[1] A personal friend of Wagner, he led the violins at the première of Der Ring des Nibelungen in Bayreuth in 1876.

He visited Australia in 1881, playing in the old Freemasons' Hall in Sydney, but though appreciated by those who attended his concerts, their number was not sufficient to make the tour a financial success.

Among his pupils were Jessie and Harold Grimson, American violinist Nahan Franko, Canadian musician Donald Heins, and the Australian conductor Aylmer Buesst.

[6] Another known violin was made by Giovanni Francesco Pressenda 1843 (Ex Wilhelmj) His 1785 Guadagnini was later owned (as "ex-Wilhelmj") by Jack Liebeck.