If you search for de Victoria's Masses or you survey the literature dealing with his music you could easily assume that he only ever wrote one Requiem - the one dating from 1605, in fact he wrote two and the 1605 composition owes a very heavy debt to the 1583 one. Whenever I tell people this it almost always comes as a great surprise to them which in turn surprises me.
Tomás Luis de Victoria was a Catholic priest a product of the counter-reformation as it unfolded in Spain. If there is one man whose music epitomises the counter-reformation de Victoria is that man. His illustrious predecessors Francisco Guerrero and Cristóbal de Morales had made notable contributions to the genre, a genre which had been a well-established part of Spanish religious culture since at least the latter part of the Middle Ages. It's not surprising that Victoria wrote more than one setting of the Requiem or the Missa pro defunctis to give it its proper title on the contrary it would have been astonishing if de Victoria had not made the composition of a Missa pro defunctis one of his earliest compositional tasks.