Here’s an interesting piece on breath support for singing, with a handy exercise to boot. It’s from Karyn O’Connor, a US voice teacher and acting coach, and her blogsite – Sing Wise.  

Correct Breathing and Support for Singing

By Karyn O'Connor, Sing Wise

In most classical singing schools, a technique called appoggio is taught. Appoggio, from Bel Canto singing, requires support from the muscles involved in inhalation, rather than those responsible for forced expiration. Essentially, we delay, slow down and steadily pace the rise of the diaphragm by continuing to use the inspiratory muscles as we sing, which happens on the exhale. This centuries old concept expressed by great teachers of the past such as Giovanni Battista Lamperti, is sometimes paraphrased 'singing on the gesture of inhalation'.

Students of voice need to learn how to extend the normal breath cycle by remaining in the inspiratory position for as long as is both possible and comfortable, maintaining a raised sternum (but not raised shoulders or clavicle), avoiding displacement of the chest (or collapse of the ribcage), and allowing the muscles of the lateral abdominal wall to stay close to the position of inhalation. This vocal posture is often referred to as the 'inspiratory hold'.

With the diaphragm kept in a lower position for longer, and with less air in the lungs to start out with, there will be less air pressure pushing on the vocal folds. Singers will notice that their endurance increases because they are no longer pushing the air out as rapidly. This will help them sing for longer on a single breath. It will also preserve their long-term vocal health. Also, with more appropriate air pressure on the closed vocal folds during phonation, the tone will sound better - more rich and easy, and steady.

Although there is evidence to suggest that this exercise had been used for a couple centuries before his time, the Farinelli exercise was named after this celebrated Italian castrato singer of the 18th century. He achieved fame and favour amongst the royals of his day because of his exceptional vocal abilities and the unmatched beauty of his soprano voice, and also became known as the 'silent breather' because he had mastered the art of the inspiratory hold (appoggio) and imperceptible partial breath renewals. With his body maintaining the posture that it had assumed at inhalation, rather than allowing the ribcage to collapse as he sang, all movement created by these tiny breaths went unnoticed to the untrained eye. Check him out (rather an actor from the celebrated Farinelli film*), singing Handel’s ‘Lascia chio pianga’ from the opera Rinaldo.

* The film itself was released in 1994 and won the Golden Globe for Best Foreign Language Film in 1995 (nominated that year for an Oscar in the same category). While portrayed by actor Stefano Dionisi, the castrato’s singing voice was given by Polish soprano Ewa Malas-Godlewska and American countertenor Derek Lee Ragin, who were recorded separately and then digitally merged to recreate the sound.

When appoggio is mastered, the singer or speaker is able to execute inconspicuous partial breath renewals, which are like 'topping off' or replenishing the air as one goes along when there is not enough time for a complete breath renewal, yet one still needs a bit more air to get through the phrase, or until one can get to the next complete breath renewal. Partial breaths are particularly useful for when there isn't a convenient spot in the song or speech, etc. to take in a breath, but one is still needed.

The Farinelli exercise is still practiced today by many students of voice. Through this exercise, the singer learns to pace his breath flow better, using it more efficiently, and keeping the diaphragm in a lower position for longer during the breath cycle. This exercise helps the singer learn to gauge how much air he'll need for a given task so that you won't 'overfill' or 'overcrowd' your lungs. It also teaches how to relax and to avoid the urge to 'panic' when it feels as though there is not enough air. It's almost like yoga, in a sense, because the singer spends several minutes focusing on nothing else but paced, relaxed, silent easy breathing. It often changes how a singer thinks about the breath, and therefore how he treats or approaches it.

Watch how to do the Farinelli exercise below, divided into three breath phases, all equal in duration: 1) inspiration (inhalation); 2) suspension or retention of the air; and 3) expiration (exhalation).

For more detailed information about correct breathing for singing, including the anatomy and physiology of breathing, please read the full article.