Each phrase you sing can and should be prepared in the breath beginning with the moment of inhalation, and it should be followed through — like you’re riding on it — until the end of the phrase.

• Determine how you want to structure a phrase in your practice.
• As you inhale, hear the phrase (the pitches, the dynamics, etc.) in your mind and imagine how it should feel to sing that phrase. Tune your throat in advance of the onset and in reaction to your imagination. With practice, this can be done quickly.
• Seamlessly integrate the end of inhalation and start of exhalation into one larger breath gesture.
• Sing the phrase by shaping the exhalation with your body to your desired phrasing. Utilize both inhalation and exhalation muscles to find balance.
• Repeat for the next phrase.

You can practice by doing simple sounds without worrying about more complex phrasing. Some body-connected sighing can start the connection. Do the steps above, just remove the music. Experiment with different inhalations and exhalations and pay attention to the resulting sound and how you feel about it.

There are, of course, smaller techniques within each of the steps above. Just the exhalation portion can be stuffed with other guidelines. But this is something of a macro overview, and the main idea is the mind/body integration around an overarching breath gesture, in which the actual sound-making is only a part.

Anyway, that’s my rough personal definition of “on the breath”.