Acoustical Instruments - a Bad Idea??

Way back when, a dealership in downtown Brooklyn kept a separate listening room, only the speakers to be auditioned were wheeled in on dollies, so no 'induced' vibrations from cones of other speakers would be involved. Made sense, right?

A member here suggested my Piano might be adding something, and I agree, you would think so, 

I set up my SPL meter on a tripod, listening position, seated ear height, CD with 29 1/3 octave test tones, play, pause, sound just disappeared, nothing carried on beyond pause at any frequency I tried. Maybe more precise equipment could detect something, 

If you don't notice or feel something is off...it's fine.

Most living room and most non controlled acoustical dedicated room will not give  much audible  difference ...

 but in a well controlled acoustical room , the material content and location of a brass instrument or of drum, cymbal may create (location matter) an audible difference...

To illustrate it the dimension of a straw or a fine tube as the neck of a resonators impact very audibly the sound in some frequencies band (location matter) ...

I have 4 acoustic and 5 electric guitars in my listening space and I don't believe they interfere with the sound at all.

I found that the strings of an acoustic guitar sometimes audibly resonate with music in the room. So I dampen them and cover the sound hole with a soft cloth.