Hm. Pondering about James Dewees

Okay, so I know James Dewees, during the Black Parade is Dead, played a roll by doing certain percussion (such as the large gong behind him during Mama) and played piano throughout in various songs (The End, the Cancer Interlude, Cancer, Teenagers, House of Wolves, etc.), but I can see him playing in songs in which there are no audiable piano parts/synth parts even.

Does anyone know what exactly he was doing during this or if he was just simply adding some sort of backing that I don't notice?