So, I thought I would start this thread for all the singers who are professionally trained (or close to it, like myself). I am a baritone 62 yrs old, and right now i am working on "Rise, Heart," the first of Five Mystical Songs by Ralph Vaughn Williams, for Easter of course. I am going to sing this with my extremely talented, professional-quality church choir. The hardest single vocal challenge for me is the opening leap of a fourth from B-flat to E-flat, forte, right into the middle of the passaggio part of my voice. The challenge is to sing it neither too open (where it sounds strident), nor too closed (where it sounds woofy or hooty). For me, I have to remember to keep the air flowing around my back teeth and sing "Ha-a-a-rt" rather than "Har-r-r-r-t" and it comes out in the right place.
What specific piece are you working on, and what specific vocal challenges?