When singing people will tell you to breath with your diaphragm, this is one of the foundations of singing used to control your breathing and produce a louder volume. Once you master this technique you will be able to hold your notes and improve the quality of your tone. The technique to sing from your diaphragm takes a bit of time to master. Start with a song that you are comfortable singing that you can practice how to sing from your diaphragm. Start out with a single note and sing it a little louder than you normally would. Pull your stomach in and try to project your voice. It will sound more controlled and it should be less of an effort to get louder volume. This is a technique known as support. Pull in your stomach tightly, this is where the support technique comes into play. Practice doing this until it feels comfortable. Breathing is essential, it adds support and gives you more volume. Place your hands on your stomach and breath in slowly. Using imagery, think about your breathe filling every part of you. Your stomach should expand. Try this same technique lying down and place your hands on your ribcage to check if it is expanding outwards.
Breathe in, pushing your stomach out and in as you sing. Practice this until you get used to it, it will feel strange at first. When you are comfortable with this movement try to sing the song again and pull your stomach in slowly and out again as you breathe and sing. Your stomach should slowly go in and then out quickly. As you pull the stomach in slowly allow a bit of room to pull it in a bit more for the next technique.
The next technique is referred to as pulsating. This method allows singers to sing at their loudest volume and make big jumps in the their pitch. It is referred to as pulsating because you pull your stomach in quickly and occasionally push it out just as fast.
To practice this use a song that has a variety of jumps in it. Use the support technique as before but when you come to a high note, a low note or a jump pull your stomach in deeply. With the jump allow the stomach to be loose for lower notes and tighter for higher notes. You will occasionally need to very quickly pull in and push out if there are a series of high notes. It can be difficult to do when the notes are fast.
Singing from the diaphragm will allow you to sing with control and power. Proper breathing will support you through your diaphragm. If you have strong diaphragm control you will improve your voice and it will allow you to hit a variety of notes and maintain them without strain. A professional singer will control the singing breath as they exhale. When you breathe out of the diaphragm and learn to control how quickly the breath is exhaled it is similar to the squeezing of air out of an accordion.
Pay attention to how your chest rises and falls when you breathe normally. Most of us use only the top of our lungs resulting in shallower breathing. By taking shallow breathes we lose our natural resonation, our sound projection and the timbre of our voices. To sing as well as you can you must learn to use your entire lung and diaphragm. We must unlearn improper breathing habits and correct them with the correct exercises for our vocals. If you hold your index finger about an inch from your mouth and exhale slowly, notice the diaphragm movement. This is the amount of breath you use when you sing, there is no need to force air out to produce a strong voice.
The muscles that surround your lungs are your diaphragm. They are attached to your ribs and their primary purpose is to regulate your breathes in and control your breath as you exhale. Controlling your diaphragm will increase your volume. When you are preparing to sing take a deep breath in, feel your abdomen extend out and try to do this naturally and comfortably. Your breath should feel warm and moist as you slowly exhale. Move your stomach naturally when you exhale, forcing or pushing air out when you are singing does not make for a good tone and can strain your vocal chords. This technique requires a lot of practice but eventually it will become a subconscious act.