First, it is important to make sure that you are relaxed and standing in the centred position (see the relaxation exercises). You cannot possibly produce a good voice if you have any muscular tension.
Having sorted out your posture and eliminated your negative tension, try the following:
Take a slow deep breath in, without raising your chest or shoulders and be conscious of your lower ribs gradually expanding outwards and upwards and the central tendon of your diaphragm (which is a dome-shaped muscle horizontally situated between the upper and lower abdomen and attached at its edges to your ribs) descending. This expands the capacity of your chest upwards and outwards, allowing a good intake of air. If you are doing this correctly, you should feel your abdomen move slightly outwards. Place a hand on your abdomen, over your navel and you should be able to feel this happening. Your abdomen needs to move in this way in order to move your internal organs out of the way of the descending diaphragm. (You may need to practise this a bit to obtain the correct movement. It is easier to feel the abdominal movement if you practise it lying on your back on the floor with your knees raised.) When your ribs are fully expanded (you can get more in there than you think) hold the breath for a second or two, feel ready to breathe out, then hiss the breath out slowly and steadily through the teeth, supporting and controlling the outward breath with your lower abdominal muscles.
Now that you know how to breathe, repeat the above and this time, instead of hissing, hum gently on the outward breath. Try to aim for a buzzing, tickling sensation on the lips. This confirms that you are resonating well. If you don’t get the “tickle”, try bringing your head slightly forward. Experiment with your head position until you find the point where you get the “tickle”. This is also a good way of confirming that your head is well balanced.
Now take another breath as before and hum down from the very top of your vocal range to the very bottom. Make sure the hum descends slowly and steadily in a controlled manner, supported by the abdominal muscles. Then try the same thing, beginning at the bottom of your range and sliding up to the top.
Now try the “siren”. Take a breath as before and hum smoothly up and down your range. If you should hit a point where the voice “breaks”, start humming just above that point and slide down and up, down and up over it until it is smoothed out. It’s just like ironing your jeans!
Take in another good breath. Start humming and turn up the volume, then open the mouth and allow the sound to carry forward on a “mmmmmmaaaaaaaaaah” sound. Always ensure the shoulders, throat and jaw are kept as relaxed as possible, providing a clear passage for the flow of air through the larynx. Do not “squeeze” with the throat.
Now, breathing as required, try the following:
MAR MAY MOO MEE MOR
PAR PAY POO PEE POR
Make sure the jaw is relaxed and opens fully for the open vowel sounds. Repeat the sequence, placing different consonants before the vowels. This helps your articulation as well as voice production. Really work those facial muscles!
You are now fully warmed up and ready to impress everyone with a voice that is a pleasure to listen to.