Pärt

In the early 1970s he stopped writing for nearly eight years and went to study Gregorian chant and early polyphony. He came out with a technique he named himself: tintinnabuli, from the Latin for little bells. One voice moves stepwise, another sounds only the notes of the tonic triad, the two lines wind around each other, and there is almost nothing else.

Spiegel im Spiegel and Fratres are that principle at its purest. The music gets labelled holy minimalism, but the stillness is not emptiness — every duration and placement is fixed exactly, and changing any of it brings the piece down. He is the most performed living composer in the world.