It's great that you love Sufjan Stevens!
It's great that you seem to know every single one of this songs, even the new ones!
It's not so great that you sang along to every song.
Although I'm not sure I would call it singing. My husband said it reminded him of Frankenstein in this old Saturday night clip:
And in addition to the "singing," you also treated us by tapping on your armrest and occasionally whistling along with the songs. You ignored all glares.
It was kind of like being treated to our own private concert.