Barrymore Laurence Scherer writes about the beautiful oratorio, St. Matthew Passon by J.S. Bach:

For more tender contemplations Bach employs the softer veiled tone of the oboe d’amore, pitched a third below the oboe. In the soprano aria “I will give Thee my heart,” a soothing pair of oboes d’amore help suggest Christ’s loving relationship with mankind.

But Bach scores one of his most telling effects by eliminating certain instrumentation: Whenever Jesus sings his portions of the narrative, his bass voice is enveloped in a gleaming tissue of sustained triads played by two violins and viola, known as a “halo of strings.”

(via Prufrock)