In the middle of the 14th century, the recently constructed Great Clementine Chapel of the Palais des Papes had a flourishing reputation for the composition and interpretation of polyphonic singing in the emerging Ars Nova musical style. In modern times, the space is still employed for musical performances. However, the acoustic conditions between the two periods vary greatly, and as such, can be expected to have an impact on vocal performances. As part of the IMAPI and PHE projects, the impact of the acoustics of the Great Clementine Chapel on the performance of a conducted vocal ensemble specializing in medieval music was examined for these two periods. A numerical simulation of the medieval acoustics was developed, based on a calibrated geometrical acoustics model of the modern-day chapel which was then regressed in time to a historically informed medieval state. Experiments were carried out with singers performing repetitions of several pieces in a Virtual Acoustic Environment (VAE) using close-mics and headphone renderings. Recorded performances were analyzed using various metrics, with objective results paired with questionnaires acquired for each VAE condition. Preliminary analysis of these results is presented in this study.