Crad's offering is very relevant. One can have good acoustics without lots of treatments, traps and padding being apparent. This is done by designing the rooms to the proper proportions, incorporating diffusive/absorbent elements into the simple modern design and, if larger elements are needed, hiding them in the walls. It takes planning and money.
That said, one should note that the concert hall and the practice rooms are all spaces for the production of music/sound and not for the REproduction of it. There are different acoustical requirements.
Nonetheless, most of us are constrained by existing layouts and, thus, need to deal with treatments that are as unobtrusive and effective as possible.
Kal