The term ‘onset’ is used to describe the way we start singing a note. There are three ways of starting to make a vocal sound.
A soft, ‘breathy’ or ‘aspirate’ onset is the result of air passing over the vocal folds before they vibrate. Sing a note to the sound ‘ha’ and you’ll hear that the breath begins to be expelled before the sound starts. This breathy kind of onset is sometimes used by contemporary soloists to create an emotional sound, but we generally want to avoid it in choirs, except of course to enunciate aspirate consonants like ‘h’ and ‘wh’.
A hard or ‘glottal’ onset happens when sound is initiated before the breath passes over the vocal folds. Pressure builds and is then released with a little explosion of breath. If you hold your breath, then release it to the sound ‘ah’, you’ll hear this hard onset. It is used when we sing words beginning with vowels in German or English, although the glottal should never be so hard as to ruin in the musical line. We also have to be careful not to encourage a glottal onset that leads to a harsh tone or, worse, damages the voice.
A coordinated or ‘simultaneous’ onset is where the breath and the sound are initiated together. Think of a gentle ‘ah’ with no breath preceding the sound, and no hard attack on the ‘a’.
For most singers, most of the time, we want to encourage a coordinated onset. Just like the beds in the story of Goldilocks and three bears, the first is too soft, the second is too hard, but the third one is just right. A coordinated onset leads to a well-supported note that is clear but not tense.
When we’re working with choral singers who have not had vocal training, we can’t simply instruct them to coordinate their onset and expect anything to happen. They won’t know what changes to make in their bodies to achieve what we want to hear. One way to encourage our singers to find a balance between soft and hard onset is to have them practise both. First, sing a repeated note to ‘hee hee hee’, allowing a lot of ‘h’ at the start. Next, sing a repeated note starting with a pronounced glottal onset to ‘ee ee ee’. You can draw your singers’ attention to the differences they’re likely to feel in their bodies with the second exercise: tension in their neck and shoulders and perhaps more work from their abdominal muscles. Then you can encourage a balance between these two extremes, singing them same repeated note ‘ee ee ee’ with an imagined silent ‘h’ at the beginning.