The core of the main organ in the Collegiate Church dates back to the organ builder Franz Xaver Chrismann in 1774 and is known today primarily as the “Bruckner organ”. The famous composer Anton Bruckner sat at the console in 1875 when this instrument was rededicated after being rebuilt by the Mauracher company. The present instrument was rebuilt in 1951 by Wilhelm Zika using the existing historical material from Chrismann (1774), Mauracher (1875) and Dreher & Flamm (1932), and has been repeatedly rebuilt and extended in the years since. With 103 stops, the instrument is one of the largest organs in Austria! Some special features of the organ are, for example, the division of the Mixture in the Positive (I) into individual Aliquots, as is actually customary in Italian organ building. Furthermore, the Swell (IV) is unusually divided into three sections (labials, trumpets and short-barreled reeds), which can be coupled separately.