As it turned out my ears might have been able to recalibrate the acoustics. There was definitely reinforcement, unevenly applied. The orchestra had a too-much-center-channel, too-much-500Hz-EQ sound. The harpsichord sometimes covered the singers' voices, and when I looked into the orchestra pit during intermission, darned if I could see a harpsichord!
Nonetheless, and despite the much-abridged version, we both enjoyed the hell out if it. I wouldn't have missed it for anything.