In his professional activity Končar dedicated particular attention to researching the sound of historical instruments as well as raising awareness of the value of tone-wood from Croatia and Bosnia used for the building most valuable instruments.
Wishing to support Croatian builders of string instruments, in 2005 he initiated the founding of the Association of Professional Builders and Restorers of Stringed Instruments in Croatia. The Association gathered builders of stringed instruments who continued the tradition of the Croatian builders Franjo Kresnik, Franjo Šnajder, Julije Penzo, Ivan Hus and Rudolf Sloković. Established with the aim of promoting knowledge and skill of building and restoration of all stringed instruments, promotion of Croatian builders and restorers as well as advising young musicians in their choice of quality stringed instruments, the Association continues to pursue its broad range of activities.
At the same time Goran Končar cooperated for a number of years with the builder and restorer of stringed instruments, Muneyuki Nakazawa, counsellor and worldwide professional for issuing certificates about the authenticity of master instruments like Stradivari’s, Guadagnini’s and others. Except supervising the works in his atelier in Tokyo, he travels all over the world in order to restore valuable instruments that are the property of leading musicians and museums. Property of Nakazawa foundation Nipon Violin is also the instrument by Giovanni Battista Guadagnini from the year 1753 on which Goran Končar currently plays. From the same collection there also come two exceptionally valuable violins: Princess Doria by Giuseppe Guarneri del Gesù from the year 1734 and the Da Vinci violin by Antonio Stradivari from the year 1714, on both of which Končar also played. For a number of years he also played on the violin by Giovanni Battista Guadagnini which the Croatian violinist and composer Stjepan Šulek left to the Šulek foundation, as well as on the King violin by Giuseppe Guarneri del Gesù from the year 1735, presently the property of the HAZU (Croatian Academy of Sciences and Art).