The organ of the Zagreb cathedral belong to the line of concert organs with romantic sound characteristics with more than 6,000 flue pipes, seventy-eight registers and four manuals. It is an instrument on which it is possible to perform literally all the organ literature, from early music all through to the most modern compositions. It is splendid both for soloist concerts and chamber music-making. The organ is considered a major achievement of organist skill and it is one of the biggest in Europe; at the same time they can be classified among the ten finest and top-quality organs in the world. As a zero-category monument of culture the organ is registered with the Ministry of Culture of the Republic of Croatia as a protected cultural good.
World-renowned organists perform at the festival solo or in a variety of collaborations with vocal and instrumental musicians.