'Songs of Consolation,' performed at Pembroke College Chapel in Cambridge last month, was the first airing in a 1000 years of a medieval tune the way it would have been.
…reconstructed from neumes (symbols representing musical notation in the Middle Ages) and draws heavily on an 11th century manuscript leaf that was stolen from Cambridge and presumed lost for 142 years… Hundreds of Latin songs were recorded in neumes from the 9th through to the 13th century. These included passages from the classics by Horace and Virgil, late antique authors such as Boethius, and medieval texts from laments to love songs. However, the task of performing such ancient works today is not as simple as reading and playing the music in front of you. 1,000 years ago, music was written in a way that recorded melodic outlines, but not 'notes' as today's musicians would recognise them; relying on aural traditions and the memory of musicians to keep them alive. Because these aural traditions died out in the 12th century, it has often been thought impossible to reconstruct 'lost' music from this era – precisely because the pitches are unknown.
They believe they've pieced together about 80-90% of the melodies. The performers are Benjamin Bagby, Hanna Marti and Norbert Rodenkirchen. Here's more: