[ronack]

Yes, I'd say the most obvious tell was the strict quantization. If they can transfer some of the timing information it might be more convincing.

[blurbleblurble]

I thought the most obvious giveaway was that the melody was not articulated at all by the robot. Aside from that, the dynamics in the robot version were completely absent. I actually didn't think it was even a very good song until I listened to the human playing it, then I kinda liked it.

[dontreact]

It might be simple to take the amount that each note is ahead or behind where it would be quantized to and model that parameter exactly the same way that dynamics are modeled.