The congregation is due to sing "The Duteous Day Now Closeth" at 2am but the Hymnathon will just be getting going. A Chiswick church is to raise money for a new organ by singing all 542 entries in the New English Hymnal without a break.
The St Michael & All Angels Church in West London estimates that it will take 30 hours to complete the non-stop Hymnathon, which begins at noon next Friday.
Beginning with "Creator of the World, to Thee", members of the congregation are invited to sing for as little or as long as their voices can muster.
Each of the hymns will be sung straight through and the time-keeping organist Oliver West expects to bring the event to a triumphant close at 7pm on Saturday night.
To ensure the pews remain filled into the early hours, the hymns are listed, hour by hour, on the church's website, so people can drop in. "All Things Bright And Beautiful" should be struck up at about 2.40am.
St Michael's is publishing a top 10, which can be followed on Twitter and Facebook, with the hymn that raises the most sponsorship money repeated as the grand finale.