I have been taking vocal lessons for about a month. My ustad makes me hum at the first black key (to the left of the harmonium) for half an hour and do 'Aaaaa' for another half hour. Basically I spend about an hour doing this boring shit and then the actual lessons start. Because of this training, my voice has deepened. I am kind of worried that if I continue to practice at the low black key, I wont be able to sing the high notes anymore. I got no intentions of becoming a classical singer. I like rock music and I took the lessons to improve my voice. Now I am worried that I wont be able to sing rock anymore. Somebody with vocal training experience please help me out!!