The present invention is for valved musical wind instruments in the musical keys of BB-flat, CC, E-flat, and F with progressive cylindrical mid-section bore or gradual conical mid-section bore expansion or a combination, not to exceed 0.85 inch bore within the first 65% of instrument length and bell throat diameters not to exceed 3 inches measured 10 inches from the bell flare, in which bass trombone tone qualities prevail. Progressive mid-section bore is novel, enhances responsiveness, and enables “early” valve placement options. A 4-valve B-flat bass valve trombone, B-flat cimbasso, or B-flat Tu-Bone is claimed, and may have a single constant cylindrical mid-section bore, or progressive cylindrical mid-section bore or gradual conical mid-section bore expansion or a combination. A valved B-flat bass inverted full double trombone, cimbasso, or Tu-Bone is claimed, as well as a “compensated” version and a full double euphonium. Invention valves may be any piston or rotary valves.