Well, every brand has their own size designations so saying "6" actually means very little without providing the actual opening in inches or mm.
That said, most brands have a #6 alto as a middle range opening so a middle range opening on baritone would probably be your starting point.
For me, the bass sax deviates a bit from that and I like a smaller opening than my bari MP so I don't run out of air. If you are not an experienced baritone player, you might consider a similar approach, i.e., if you play "medium" facings on alto and tenor, going just one increment toward less open for a first bari MP.
A forum community dedicated to saxophone players and enthusiasts bought to you by Harri Rautiainen. Come join the discussion about collections, care, displays, models, styles, reviews, accessories, classifieds, and more!