Singing songs and playing tunes are very different things, and as I understand it, for most of the time people have been doing these things, these have tended to be separate. To oversimplify things, the songs are for listening to, the music is for dancing.

For me, the best singing is singing without any musical accompaniment.(So is the worst.) And the best tunes are tunes played without anyone singing. And the best kind of musical activity is the sort of session where the tunes are interspersed with unaccompanied songs, with people hushing up to listen to them.

But putting the two together is what people seem to find more accessible. And it is a lot of fun, and can sound pretty good.

But what tends to happen is that the musical accompaniment takes over and drives the song, and that can destroy the pacing of many songs - it's not so much a matter of the singer pausing to remember the next line (though it can be that) - it's more a matter of the listeners being allowed a chance to reflect on it and take it in before the next line is given to them.

I think Gary T was right to suggest that an instrumentalist who doesn't sing songs is going to find it hard to provide the kind of accompaniment that doesn't put a song off-balance. Telling stories might give something of the same understanding of the way that the meaning has precedence over the sound.