Very classy! It set the mood well and never strayed from it, there's a good sense of a larger world that exists outside our taxi full of people and demons going about their daily lives. I expect a lot or maybe all of the characters are references, but I only caught The Devil Went Down to Georgia because I'm not very cultured.
My results were 132 soul coins and I did identify where the soul gem had gone, though I'm not one hundred percent sure it was right to disclose that information. I may also have lost my immortal soul, and on the very first turn...
I think dividing the player's attention between dialogue and a rhythm game is a great way to simulate the multitasking of driving a car and carrying on a conversation. I'm super bad at multitasking, by the way!
A couple of notes, the falling arrows were skewed to the right for me instead of landing on top of the indicators, which I can at least use as an excuse for every miss I made. Also the text jumps a round a lot when it's being written out, I suspect this is because you've set it to be centered in the box rather than aligned to one side, though I'd also understand if you wanted it to display that way. ALSO! I was hoping I could pick incorrect destinations for my passengers and see what would happen when they showed up at the wrong place, but that's really just a random thought on my part.
Really, really well done!