Autotune the samples? Lots of software available to do that, but then you get "Intensive Hair Unit" https://www.youtube.com/watch?v=8coX8VkUKY8
I think Bicycle creator's intent was more to demonstrate the "Musical Talent of the Crowd" - the creepiness was a bonus.
Seriously, part of choral performance is you (as a singer) need to constantly adjust your pitch and timing with others to produce harmonious output.
This would be far more interesting if such an effort could be done based on the individual samples by manipulating the audio in real-time.