You'll have to invite us for a site visit.

I suspect that you won't need much for amplifying sound but you may need something for balancing voice with instruments.

What is the composition of your walls in terms of whether they are solid, hollow, or insulated?

Same question for ceiling.

Minimizing the "bounce sound off flat surfaces" by slanting room walls sounds useful.

Quilts might be nice as hangings (on ceilings or walls), if you have them or can afford them, to absorb sound.

Cheerily,
Charley Noble