Two scholars at Stanford have joined forces to recreate what a Christian choir might have sounded like inside Constantinople's Hagia Sophia before it became a mosque in the 1400s.

Prof. Pentcheva went to Turkey, got permission to visit the museum after hours, and after setting up microphones and recording equipment.

That single sound–its echoes, resonance, and tonal qualities–provided data that was analyzed by computers and turned into an algorithm that could be applied to other electronic recordings. And thus the sound of a choir singing in the 13th century could be recreated today.

Watch Cappella Romana perform live with a virtual Hagia Sophia audio filter:

The following clip from NPR goes into more of the background and includes the sound of a balloon popping here and what that balloon sounded like in the Hagia Sophia. And then the clip plays the modern historical music group Capella Romana singing a 13th century Byzantine chant, which would have been part of the Divine Liturgy in the Orthodox Church of that day.  We hear the studio version, which sounds very good in itself.  And then we hear it with the Hagia Sophia filter, whereupon it becomes transcendent.

Listen for yourself: