Artificial Intelligence + autoarranger technologies.
"We believe that it is possible to learn the underlying regularities existing between piano scores and their orchestrations by notorious composers, in order to automatically perform this task on novel piano inputs. ... We introduce ... the Live Orchestral Piano (LOP) application, which is the first software able to provide a way to compose music with a full classical orchestra in real-time by simply playing on a MIDI piano".
Live Orchestral Piano, a system for real-time orchestral music generation
Léopold Crestel, Philippe Esling
http://arxiv.org/abs/1609.01203