“On the evening before the broadcast, it was discovered, by Houston, that the arrangement wasn’t working, and the rehearsal ground to a halt. … With none of the musicians in the hall (including Bill Conti, the longtime conductor of Oscars ceremony) able to riddle out a solution, Houston identified the offending chords for the orchestra and created a new arrangement on the spot. The room watched her in awe.”
Cinque Henderson - The New Yorker, January 27, 2016