Madelaine performs the soprano solo in the duet "Christe eleison," as part of a complete performance of Bach's B Minor Mass. Please note: Although American Bach Soloists repeats the performance on August 12, Madelaine will not be singing in the August 12 performance. 

From the American Bach Soloists website:
An annual pilgrimage for many concert-goers, ABS’s performances of the work that represents the pinnacle of Baroque music are legendary, especially in the passionate and dedicated hands of ABS Academy faculty and participants.