I also found this hilarious quote about 16 bars in an audition:
So, the "bars" thing is tricky; it harkens back to a day when songs were generally written in 3/4 or 4/4, had nice 16 bar intros, 16 bar verses, 16 bar choruses, 8 bar bridges. Music has gotten more complex, thankfully, but the adherence to bars has not evolved. These are my views on what they "really" mean when they say "x bars":
32 bars- 60-75 seconds, or verse and a chorus. Show a full journey, going from point A to point B.
16 bars- 30-45 seconds, or just a chorus. Show emotional and vocal range if not a whole journey.
8 bars- 15 seconds, half a chorus. I can duz high note? kthxbai.
If they ask for 8 bars, they don't really care about the semantics of it; 4 bars or 12 bars, it doesn't really matter as long as you're in and out and that what you sing *feels* like two short four-bar phrases. I'd personally advise against focusing on the letter of the law (i.e. altering your music so it's a "strict" 8 bars) and focus instead on keeping your cut around 15 seconds.
Also, my improv classes are hilarious and so much fun. I start choir rehearsals again tonight, too. I am busy all the time, but I guess it's good. It gives me "something to live for" in these cold, dark months.