J. S. Bach and Percy Grainger, and 6 pianos. And 6 pianists: Marc-André Hamelin, Angela Cheng, Angela Hewitt, Jon Kimura Parker, Janina Fialkowska and André Laplante. Actually the orginal Grainger transcription/arangement of BWV 540, Toccata in F,
calls for 3 pianos, 3 pianists, and 6 hands, but the score allows doubling of parts to 6 pianos, 6 pianists, and 12 hands. I hope I did that arithmetic correctly. Six pianos make a lot of sound.