To clarify, the difficulty wasn't in creating the animations, but the content development side of cutscene composition, camera work, timing the action to the music, getting the lyrics to appear at an appropriate time.
We commissioned a singing idle animation and a second to trigger as needed for flourishes. We didn't go as far as creating unique lip synced animations for each voiced line. If you got the impression we did, that's a good sign!
Shout out to Mod Zura for creating the musical finale and especially his epic camera work.
My contribution came in tuning the timing to make the most of what we had (especially later when the voiced track became available) and getting obsessively perfectionistic about trivial details.