"But at midnight Paul and Silas were praying and singing hymns to God, and the prisoners were listening to them."
This well-known verse (above) has several intriguing elements to it. First off, Paul and Silas are up late (at midnight). Secondly, they are praying and singing "publicly," and out loud--not at all concerned that others would hear them. Lastly, the other prisoners were "listening" to them. They were giving attention to what was being sung and said.
I can imagine that those two guys may have had gravelly singing voices; but it's also likely that what they sang and prayed was a great source of ministry to all who heard them. Let us remember that the Christian faith, the true religion, is not a "private" matter, as the godless would hope it to be; instead, our doctrine is totally "public," and it should fill the world even as "the waters cover the sea."
[Puritan quote of the day: "Is your sin as big as God, as big as Christ?" --William Bridge, in "A Lifting Up for the Downcast"]