Lessons six, seven, and eight are about registers, and they go in the order most singers experience them: the low, speaking part of the voice first, the high part second, and then the join between them. Registers are where a lot of beginners get stuck, because the words are confusing and the teaching methods differ.
Chest voice is the register your speaking voice lives in. The name is misleading (nothing much happens in the chest) but it stuck. It is the base of most pop, rock, R&B, and musical-theatre singing, and it is the foundation belting grows out of. This lesson is about strengthening it without the one mistake nearly everyone makes, which is to confuse strong with loud.
What to notice
Two exercises. "Mum" on a 1-3-5-3-1 arpeggio in the lower-middle part of your range, and "mah" stepping down 5-4-3-2-1. Both are scored.
On "mum," the target sensation is a full, connected sound that feels like confident speech. If your throat tightens or the sound gets pressed as the arpeggio rises, you have crossed from strong into shouted. Back the volume off and let the "m" do the work of starting each note.
On "mah," let each note land rather than reaching for it. The bottom of the range is where a lot of singers add weight to feel powerful, and it is exactly where added weight makes the pitch sag. The per-note breakdown will show you if the low notes are going flat, which is the tell.
These exercises sit low on purpose, so the keys mostly stay below your break (tenors may feel the top key touch it). That is by design. The passaggio gets its own lessons.
What done means
Sing both exercises through and log them. You are done when "mum" feels spoken all the way up and the low notes on "mah" are not going flat.
For your routine, add one, not both, unless your voice sits naturally high and the low register is the part you never use. "Mum" is the more general pick.
The exercises
Chest Voice Mum
About this exercise
A grounded 1-3-5-3-1 arpeggio on a full 'mum' in the lower-middle register. The closed 'm' onset and open 'uh' vowel keep the tone connected and chesty without pushing, building a strong, carrying chest voice. Stay relaxed; let the sound feel spoken, not shouted.
A descending 5-4-3-2-1 on an open 'mah' that strengthens the bottom of your range. Releasing down into chest with a full, supported tone trains a confident low register without weight or strain. Let each note settle rather than reaching for it.