Acoustical Instruments - a Bad Idea??

Strings by themselves shouldn't be much of an issue.  Now instrument bodies, like an acoustic guitar, violin, upright bass, any kind of drum, or a piano, those can be problematic.  The issue isn't the strings as much as the resonance cambers of the instruments. They don't care where the sound energy comes from (strings or from the speakers across the room).  The energy is going to enter the resonance chamber, bounce around inside, get changed around, and then dumped back into the room.

My experience is, probably not a problem, but easy the throw a blanket over if need be...

I have a virginal, two violas, three violas d'amore (all in cases) in my listening room. No issues whatsoever. Bowed stringed instruments are typically stored in cases when not actively used. 

Also consider that in acoustic concerts there is no problem with unplayed instruments at any particular time. 

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.