I would personally constitute using ANY instrument (acoustic guitars, hand drums etc) on the MRT as nuisance.
That is why perhaps an all-vocal performance would be as far as one could go. Then again a straight out everyday acapella with vocal harmony and stuff is still bland by my books.
These guys, on the other hand, they become instruments themselves. Which make them REALLY something. Check out their other videos and you'll see why.
I personally think that, if there were ever anyone want to try this, it's best to start out with some place more open first eg Starbucks at Plaza Singapura.