This warm-up is great for developing fluidity and good intonation. It also sounds really cool if you get a group of four friends together and have each person sing a part, thus creating harmony. You can also use this exercise alone, by just singing the scales. If you do it with a group, during the scale descent sopranos stay on 8, altos land on 5, tenors on 3, and basses on 1. (I'm the female voice in this one).