I do exercises for mix voice. My teacher gave them to me. I have to do sirens on "soo" (oo as in food, basically u with 2 dots on it). I also need to exercise lip trills. I tried connecting these, but I can't. I did it a couple of times, but no more. Should I just try, or are there some tips? Oh, I only connected it with sirens, and not lip trills. What should I do?