This is an associated paper to a previous one, “Favorable clarity, sound strength, and spaciousness as well as overall acoustical quality of concert halls measured in a 3D synthesized sound field,” Acoust. Sci. & Tech. 46, accepted (2025). Anechoic music was reproduced by a virtual orchestra in concert halls and was recorded at audience seats. Four music excerpts were chosen. By a fourth order Ambisonics playback in the laboratory, 21 music experts judged the loudness–perceived sound strength–of the presented sound. The results confirmed that constancy was held for loudness judgments. The early to late reverberation energy ratio was found to be a plausible acoustic physical quantity as a cue of constancy.