The first organ was inaugurated on March 7, 1850 by Damis Paul, organist at Montreal's cathedral. The instrument had been partially installed in 1848 for Bishop Guigues' consecration. Joseph Casavant built an 18-stop instrument (1,063 pipes) and placed it in a case that was later sculpted by Flavien Rochon in 1871. The instrument was restored by organ builder Louis Mitchell a few years later. Casavant's sons completely reconstructed the organ in 1892. At that time, it was a 52-stop instrument with over 3 manuals and pedal. The instrument used an electro-pneumatic action. The main section of the organ is located in the rear gallery while a second organ, a 17-stop choir organ over 3 manuals and pedal, is located in a gallery over the sanctuary. Both organs are played from the console located in the rear gallery. This instrument is considered one of the three outstanding instruments in the history of the Casavant firm, the others being the one in Notre Dame Basilica in Montreal (1890) and the one in St. Hyacinthe Cathedral (1885).