At the age of 9 Jukka Harju found the horn and two years later he performed Mozart's Horn Concerto in Eb KV447 at a concert in Dublin broadcasted for TV by European radio stations. The blitz start went on to the studies in the Sibelius-Academy in Helsinki with Kalervo Kulmala and later in Vienna University for Music and Performing Arts with Roland Berger, principal horn of Vienna Philharmonic Orchestra. Harju was sought after by the Finnish leading orchestras as well as the EU Youth Orchestra and Gustav Mahler Youth Symphony Orchestra led by Claudio Abbado.
Since then Harju has succeeded in several music competitions. By winning the Lieksa International Horn Competition 2005 he was nominated as a Brass player of the year 2006 in Finland.
On 2008 Harju settled on the leading chair of the horn group in the Finnish Radio Symphony Orchestra. Before that he was a member of Tampere Filharmonia and Helsinki Philharmonic Orchestra. On the side he has appeared as a guest principal horn in l'Orchestre Philharmonique de Radio France, Swedish Radio Symphony Orchestra, Royal Stockholm Philharmonic Orchestra, Oslo Philharmonic Orchestra, Bamberger Symphoniker, Chamber Orchestra of Europe and Comics Oper Berlin.
As a horn soloist Harju has performed more than 50 concerts, among others with FRSO, Helsinki Philharmonic Orchestra, Lahti Sinfonia, Tapiola Sinfonietta, Ostrobotnian Chamber Orchestra, Tallinn Chamber Orchestra, Dala Sinfonietta, Haydn Orchestra Bolzano etc.
Classical and romantic era music is on his main focus, but Harju is familiar with fresher music too. In his repertoire can be found concertos by Wolfgang Plagge, Pehr Henrik Nordgren, Oliver Knussen as well as the concertos written for him: Kirmo Lintinen Concertino (2008), Aulis Sallinen's Five female portraits for horn, soprano and orchestra (2013) and Osmo Tapio Räihälä's Horn Concerto (2016).
Harju has been entrusted with the jury in the 4th Lieksa international horn competition (Holger Fransman in memoriam), Juozas Pakalnis International Wind Competition and the Verbier Festival Orchestra audition jury. Year 2010 Harju hosted the 18th Nordic Horn Seminar in Turku, Finland. He has taught in Metropolia University for applied sciences and for now he has a horn class in Sibelius Academy at the University of Arts Helsinki.
In a role of a chamber musician, recitalist or teacher Harju has act in Italy, Germany, Lithuania, Sweden, Norway and Iceland - and even further in Japan and United States. When not playing, Harju's time is devoted to compositions, arrangements and work as a freelancer director.