you can use stryofoam panels and hang them from the ceiling. I have also seen a music teacher use the stryfoam egg cartons, tied or stapled together to form a panel. That would actually work best (but be tons of work and take a while to collect) because the sound catches in the "pockets". One thing, check with fire regulations about what you can hang from ceilings. I would thing if you used stryofoam insullation panels hung from wire, that would be ok.