Complex sentence: Most recordings of the cantata, however, feature mixed choirs: an exception are Nikolaus Harnoncourt and Gustav Leonhardt, who used all male voices in their set of the complete cantatas, and here deploys boys' voices as the top lines of the choir.
Split into simpler sentences: Most recordings of the cantata, however, feature mixed choirs: an exception is Nikolaus Harnoncourt, whose complete complete set of the cantatas made with Gustav Leonhardt uses all male voices. For this cantata Harnoncourt deploys boys' voices as the top lines of the choir.