Breathing comes second because it is the thing most beginners are told about first, and usually told wrong. "Breathe from your diaphragm" is repeated so often that it sounds like a technique. It is closer to a feeling. The diaphragm is the muscle you inhale with, and it is mostly passive as you sing out (classical appoggio teaching argues for keeping some inhale-muscle engagement; the guide covers that). What you control on the way out is how steadily the air leaves, and that steadiness is close to what most singers mean by support, though each method defines the word a little differently.
The guide behind this lesson goes through the anatomy and the main exercises singers use. This lesson picks one, the messa di voce, because it isolates the skill without anything else to think about.
What to notice
The exercise is one held note. You start it as quietly as you can, swell to full volume, and come back down to almost nothing, all on the same pitch. The piano gives you the note and then holds a chord under you. There is no scoring on this one. Loudness on a steady pitch is something the app cannot measure well, so it plays along and you judge by ear.
Two things to listen for. Does the pitch creep sharp as you get louder? It usually does at first, because pushing more air also pushes the pitch up. And does the sound wobble or cut out on the way back down to quiet? The quiet end is harder than the loud end. Getting softer without the tone falling apart is the actual skill.
Try it three or four times at most. It is tiring in a way that is easy to underestimate.
What done means
You have done this lesson when you can get through one full swell without the pitch jumping and without the sound dropping out at the quiet end. It does not need to be pretty. The full guide has more on where teaching methods disagree about breath, and it is worth ten minutes if you have been given conflicting advice before.
The messa di voce is a fine routine exercise, but it is not a warm-up. If you add it, put it after the exercises from lessons three and four, once your voice is already moving.
The exercise
Messa di Voce
Follow-along, not scored
About this exercise
On one sustained pitch, swell from near-silence up to full volume and back down to near-silence in a single smooth arc, the classic messa di voce. The classical bel canto test of breath control (appoggio, the Italian-school coordination of breath and tone) and of dynamic command.
Vocal breathing exercises explained with the science: appoggio, SOVTs, and the messa di voce. Practical drills for pop, rock, R&B, and musical theatre singers.