We have just come back from South Yorkshire for the carols. I sing with a West Gallery Choir and understood that the West Gallery style of the carols was taken out of the churches to be replaced by the church organ. I was amazed to find that an organ had been placed in the Dungworth pub for the carols???Fortunately the organist had to go early to play in Sunday school so we did get some unaccompanied singing. I find it much easier, when searching for harmonies as I go along, to do this without an instument present. There were not so many people joining in however when it was unaccompanied. Thinking about it in this way perhaps you have to have a really good ear to sing tune or harmonies without instruments, and so instuments make it more acessible to everyone.
Like many here, I can't play 2 instruments at once, and as far as I can see the voice is an instrument.
On the Gospel note - the BBC are taking 24 singers and turning them in to a Gospel Choir the first weekend in December, to be played on Sunday morning 28th December Heaven & Earth show. It will be interesting to see how they get on.