Welcome to Module 3. Look at what you are carrying in: a fuel line (the hiss), an aim (the siren and the merge), an ear that knows its intervals, a body that keeps the beat, a mapped range, and a Songbook with a band that plays in your key. This module makes that working voice sound rich — and it starts with the strangest thing your voice does.
Try it right now: sing a gentle siren from your lowest comfortable note to your highest, Module 1 style, at conversation volume. Somewhere on the way up, most voices hit a spot where the sound suddenly flips — a little yodel, a squeak, a jump from full to fluty. Singers have been embarrassed by that flip for centuries. By the end of this lesson it will stop being embarrassing, because you will know exactly what it is: a gear change.
Two gears, one engine
Your vocal folds — the two vibrating bands from Module 1 — have more than one way of vibrating.
For low and middle notes they vibrate thick and full, like a heavy guitar string. This is the voice you speak with. Singers call it chest voice: put a hand flat on your chest, say a firm "hello", and feel the rumble land right under your palm.