A postlude is a piece of music played at the conclusion of a service or ceremony. It typically follows the recessional (the exit of the clergy) and continues as the congregation departs. A postlude, being instrumental, doesn't require participation from the congregation in the same way a final hymn does. As such, it provides a moment for individual reflection without the need for communal singing. Personally, I see the postlude as a final musical offering to the Almighty. Colin wrote this very accessible piece and has made it available instantly via PDF on his website below.
I recorded this on the newly released Mátyás II sample set (Inspired Acoustics). It's a 110-stop 1909/1984 Rieger-Kloss symphonic organ of the Notre Dame of Buda (Matthias Church), Budapest, Hungary. For further information, please visit the page here: https://www.inspiredacoustics.com/en/products/matyas2
For the Hauptwerk enthusiasts out there, I have loaded this in 24-bit quality with samples truncated to 250ms and have applied both the supplied reverb files (close/distant) to achieve this glorious sound.
Score: https://colintheorganist.wixsite.com/home/compositions
Colin's rendition: 