So i used to stutter really bad. Singing helped alot because it forced me to control my diaphragm and made it stronger along with my vocal chords. It helped with my rhythm of speaking as well. Im not 100% but I'm Waaaay better than when I was younger for stuttering. It worked for me but idk if it's scientifically a proven method to help so take it with a grain of salt. Also if you try it out and doesn't even matter if it's good Just belt that shit out as hard and loud as you can in your car ride to work. Works wonders.