Along the side walls you probably would want diffusion and not reflection
Do you mean on the stage?
The side walls along the amfi can not be touched, this treatment is completed. There has been an acoustic consultant involved before the building started.
The present reverb time is the best compromise, but sometimes the compromise isn´t good enough.
The musicians feel that the stage is too dead so sometimes some of the orchestra are sitting in front of the stage, around 1,5m from the first row.
I wold also like to hide the side walls on stage, thats why I thought reflective legs and reflective back curtains could be a good idea.