Breathing through your nose, as opposed to your mouth, when vocalising (or playing a wind instrument) means that you have more breath to vocalise or play with. It’s worth experimenting a bit with this in terms of vocalising scales or even reading a passage out loud from a book and seeing how often you take a breath through either your mouth or your nose. Gasping for breath was one of the three things which FM Alexander noticed he was doing before he came to speak, something he observed in the mirror with which he surrounded himself to determine what exactly was causing his loss of voice.