I started with weekend Warrior(I am an absolute beginner). In my second week now, I noticed 2 progressions.
-I am a member of a philosophical/meditation organization, in the meditation part, one person sings a vowel sound and then together a few times.
Ons of the members is a musician and if he sings it is always on tone and he can hold the vowel sound seconds more than I. Today the sounds were in the A-tone and usually I have difficulties to find the right tone and to hold it. today it wasn't a problem + the singer stops and I had still breath enough for a few seconds. I can only conclude that the exercises helped and that my breathing is improved.
-I have one song that I want to learn to sing, so I record myself a few times in a week(I only sing a few lines). Before and the first days I started this program it was false and not in tone. Today it is a lot better, not perfect, but not so bad anymore(just practice needed on one or two notes).