Humming is a great way for developing vocal coordination–that is, getting the right amount of air flowing with the right amount of vocal cord tension to produce a clear tone. It also helps you focus on the resonant spaces in your chest, throat, and head (which can feel funky if you haven’t really noticed it before). It’s also a great way to warm up.
So first things first. When you hum, start by placing the tip of your tongue behind your bottom teeth. And be sure to leave it there. As you hum, play with the amount air you use as you go up in pitch. With some practice, you’ll notice that it’s easier to produce a good tone on the high notes with less air. Be sure to keep your mouth, tongue, and neck very relaxed.
So what should you hum? Anything, really. But if you are practicing scales or intervals, then humming is a great way to work through those to help remove the areas where your voice may be breaking. If you’re not working through scales or intervals, then hum through any songs you are learning.
If you notice your voice tensing up as you approach high notes (yes, it can happen even with humming), concentrate on staying relaxed and using less air. It’s okay if the tone isn’t clear at first. You need to unlearn the habit of tensing up first, before you can develop a clear ton
How do you know if you’re Humming correctly? Do a “Hum – Check”.
- Can you hum all the notes within my vocal range without difficulty, and them for a longer period of time?
- Does the humming note sound clear?
- Is the facial expression during the humming “joyful” and relaxed, or rather tense?
You can apply humming to many scales, songs etc. for warming up, but here’s a simple warmup to get you started:
source: http://www.howtosingbetternow.com/2009/05/singing-tips/tips-on-how-to-sing-humming