Marco Enrico Bossi is the best-known Italian composer of organ music and virtuoso from the turn of the 19th to 20th century. He also composed secular and sacred choral music, ranging from unaccompanied settings to large-scale oratorio. In his Missa pro defunctis op. 83 for mixed chorus with harmonium or organ accompaniment ad libitum, he encapsulated the aims of the Cecilian movement, the 19th century movement for the restoration of sacred music, in a convincing musical form. Bossi wrote a first version of the Requiem Mass in 1892/93 with a colleague; in 1906 he replaced the other composer’s sections with his own. This final authorized version has now been published in a first critical edition. One of the essential sacred choral works by Bossi, this Requiem deserves to be rediscovered.