Let's talk about the diaphragm. You can't move it on your own, you can't control it, it is simply a muscle which moves when you breathe. Instead of focusing on this muscle it might be better to focus on slowing down your breathing and increasing your lung capacity.
While breathing definitely matters when it comes to training your voice try not to get too caught up in this. Knowing your instrument and how to manipulate it is the trick to improving your voice and improving it fast!
Your voice is your portable instrument, and it's free.
How did it take someone 4 * 30 minute lessons to learn how to sing? By learning how to move their voice: learning how to feel their larynx (Adams apple), learning how to feel their vocal cords opening and closing, and learning how to control the sounds they were making. No, this person did not learn to sing like Beyonce or Lady Gaga in 4 lessons, but they did learn how to pitch, and they did learn how to shape their voice. Most of us are impatient to develop new skills quickly, and while we can begin to see the budding of great vocal skills in a relatively short amount of time, it takes work to see them bloom. Unfortunately, when things require work we back off, we shy away, we think to ourselves that we can't do what we wanted, we can't do everything we put our mind to because we aren't good enough, or we are embarrassed at putting ourselves forward.
Singing is a vulnerable instrument to use. It's deeply personal. It's you. I'm here to tell you that the singing journey doesn't have to be demoralising. You can put your mind to improving your singing skills and you can enjoy it. It doesn't have to be a journey where you hear no difference. There's no need for it to be a journey where you feel like giving up as soon as you started.
It doesn't have to take years, or even months, to notice improvement. All it takes is work, commitment and some enthusiasm.
So, to begin your singing journey all you have to do is become familiar with your voice. What is going on inside your mouth when you laugh? What does your tongue do when you yawn, cry, or whisper? What's happening with your larynx (Adams apple) when you hiccup, shout, sing high notes and low notes, belt out Christmas carols or make loud conversation at Christmas parties?
Understanding and becoming familiar with your voice and its habits will propel you so far forward in your journey you will be impressed.
I hope you enjoy this Christmas season and obligatory belting out of Carols and making fun of some terrible Hallmark Christmas movies!