Yes, we record or videotape each violin individually, so buyer can see or hear how the violin sounds under "real" performance setting.
We do not add after effects to the audio, simply way too time consuming and lose the purpose to faithfully represent each instrument's character. What we do is using "instrument" mic with total flat frequency response, so to capture the sound accurately; direct into the computer/software with no further editing. Usually the player would record the track within two takes, not knowing the instrument beforehand. Maybe not a perfect performance, but suits the purpose of auditioning the instrument.