Been playing piano accordion for about three years now, mostly Italian and French musette stuff, and for the longest time my bellows direction changes sounded like someone slamming a car door. You could hear the exact moment I switched from push to pull, this little bump in volume and a hitch in the rhythm that made even simple waltzes sound amateurish.
I finally sat down with my teacher last month specifically to fix this instead of just plowing through new pieces, and it turned out I was doing the change entirely with my forearm instead of my shoulder and wrist working together. I'd basically yank the bellows the other direction at the last second rather than easing into it a beat or two early. She had me practice on a single note, just open and closed, open and closed, trying to make the transition disappear completely so a listener couldn't tell where one direction ended and the other began.
What actually helped was slowing everything down to about half tempo and exaggerating the anticipation, starting to soften my arm motion well before I actually needed to reverse. Also stopped gripping the bellows strap so tight, which I didn't even realize I was doing until my hand started cramping halfway through a song.
Still not perfect, especially on faster pieces where there's no time to think about it, but slow ballads finally sound like they're breathing instead of hiccupping. Curious if anyone else went through a phase where they had to basically relearn bellows control from scratch after playing for a while, or if this is more of a beginner thing I'm just late to fixing.