Gaelic speakers of Scotland have preserved the "old way of singing" metrical psalms. This kind of singing prevailed before the introduction of congregational harmony singing into English and New England churches. It features unison singing, lining out by a leader, free ornamentation, and very slow tempos. This could be a description of Primitive Baptist singing in this country, but the two sound very different!
Here's a video from the Isle of Lewis. You can get some of this music through iTunes–search for "Salm" there.