they say there are no weird questions but this must be one of those which are getting really close
you take a very bright mouthpiece then you want to darken it (instead of getting a darker piece).
Anyway, the reed may help you getting a less projective sound BUT really the biggest change in tone comes from you.
That is if you are in control of YOUR sound as opposed to let the equipment,ent do what you are supposed to do
Many players blow directly into the mouthpiece doing little to the sound and letting the equipment do SOME of the work for them
Really you can play a rounded subtle sound (through the whole range but that requires a lot of control) even on a bright piece.
I plan now for many years on a Brancher J27.
This mouthpiece can play bright if you want to and much louder If you CAN (you need to work on this won't come to you without work!)
Some time ago when I played in a workshop " orchestra" there was someone whom liked my sound and decided to buy the same mouthpiece, se was horrified that she couldn't get the sound that I got from the same mouthpiece ( let's not even discuss reeds, the point isn't that), she had an harsh and forward sound which wasn't " round" and filling space as in subtonic sound .
The thing is perfectly described by Don Menza in this famous video. Pay attention to what he says and more than anything learn to work on sound production.
YOU are the most important factor, way more than a reed or other, to achieve a sound which, first of all, has to be in your ears ( and brain)
watch, listen and DO WHAT HE DOES really