Jan Harshagen was born in 1960 and his father was principal oboe in the Frysk Orkest. Jan started studying the horn at the age of 11 with the principal horn of the Frysk Orkest. His first appearances as a soloist date back to his time with this orchestra, with whom he performed, amongst other works, horn concertos by Mozart, Telemann, Flosmann and Strauss. During his time at Leeuwarden's grammar school, Jan became a member of the regional and national youth orchestras, with which he often went on tour.
In 1980, he entered the Amsterdam Conservatoire to study with Vicente Zarzo, solo horn with the Residentie Orchestra The Hague. In his second year, he joined the Amsterdam Philharmonic Orchestra and also became one of the principal horns of the European Community Youth Orchestra (ECYO). With the ECYO, he performed with world-renowned conductors including Sir Georg Solti, Daniel Barenboim, Claudio Abbado and James Judd.
When the COE was formed in 1981 by alumni from the ECYO, Jan was invited to join straight away but had to decline this offer because of his position in the Amsterdam Philharmonic. He eventually left that position in 1989 in order to have more availability for the COE, with whom he had been performing as a guest since 1983.
In parallel to his work with the COE, Jan performs with several dutch orchestras, including the Royal Concertgebouw Orchestra. As a member of the ASKO-Schoenberg ensemble, he also takes part in contemporary music projects. He has performed as a soloist with a number of orchestras, such as the Noord Nederlands Orkest, the Nederlands Ballet Orkest, the Promenade Orkest, the Amsterdam Sinfonietta and the Solisti Veneti. He is also a very keen chamber musician.