Bach 4 vs Bach 6½A (small shank)
The Bach 4 has a wider cup diameter, the Bach 6½A (small shank) features a deeper cup.
The taper behind the throat leading to the shank. Affects projection and tone character.
Mouthpiece A
Bach 4
• Baritone / Euphonium
Backbore—
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 6½A (small shank)
• Baritone / Euphonium
Backbore—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Which is better?
Neither mouthpiece clearly dominates the other — the right choice depends on your embouchure, playing style, and the sound you're after. Try both if possible.