As I understand it, Luther used only one secular song [which is the folk tune used in VOM HIMMEL HOCH]. In all that I've read, this one tune is the only one that Luther used which was being sung in a secular context, and when he discovered this, a new tune was substituted.
It seems to me that the popular myth that Luther used the bar tunes of his day is based on the misunderstanding that a bar tune is a tune sung in a bar, but actually it is a tune with an AAB structure, which is known as bar form, of which Luther, we are told [haven't checked], used many.
Those who want to say that Luther and the Wesleys used secular tunes don't usually cite any evidence, but simply make the assertion.
Having said this, I'm not against using pre-existing secular music in every case, but do see a problem with using a song which is currently played in a strip joint in church next week.
We sing hymns to folk tunes which Vaughan Williams set, we sing a Christmas song to Greensleeves [a song about a prostitute] and to The Tune from County Derry [which is popularly called The Londonderry Air or Danny Boy]. I don't think this is a problem if the tune doesn't make people think of prostitutes or give them maudlin thoughts of Ireland [in a song by a non-Irishman who never even visited Ireland!]
One Sunday many years ago when I was playing the organ in a church in Brisbane [in fact, the first Church of Christ in Australia], I played The Battle Hymn of the Republic at the conclusion of the service.
A little boy came out to the organ and sang in a loud voice
Little Peter Rabbit Had A Fly Upon His Noseto my great embarrassment!
Little Peter Rabbit had a fly upon his nose
Little Peter Rabbit had a fly upon his nose
And he flipped it and he flopped it
And it flew right away
Another instructive experience, also in Queensland Churches of Christ, was in the opening convocation service for our college, held unusually in a large Presbyterian Church in Anne St, because there wasn't a Church of Christ big enough.
We weren't used to pipe organs in church, as we tended to have small electronic ones or pianos. As the organist played, I had warm spiritual feelings [whatever they are] as I listened to him play great classical organ music in his pre-service voluntaries.
A little boy from the country squealed "Oo! Sounds like a horror movie!"
Which shows that one man's Bach is another man's Boris Karloff!
David McKay
www.aussiemusician.blogspot.com