ok. i export a keyed sequence that has one track with the main chroma key, and another track of the same video above with a matte inside the body to keep the 'insides' from being keyed out. looks great in the canvas and i painstakingly key-framed the upper matte over 4 hours!!!
wonderful, except i want to export the sequence as Animation, millions of colors+, and to keep the alpha, i do NOT render the timeline before export (as i think is the only way to keep the alpha...). BUT the exported movie does NOT keep the upper track, so there are holes in the key. what the what???
any big brain know what i have done wrong?

oh. never mind!
SOLVED: i didn't disable/delete the chroma key in the top video track. but still confused as to why the canvas did not show the holes in the key? weird.