The 42AFG features the ‘Infinity’, Bach’s proprietary axial-flow valve, and the 8½-inch one-piece Bach 42 gold brass bell that has defined the symphonic trombone sound for generations.
These features, plus its large bore combined with an open wrap F-attachment offer a warm sound, great projection, and an efficient and open feel.
* The axial flow valve began development in the late 1970s as a means of reducing the distortion to the air column created by traditional rotary valves, particularly on trombones. It was the brainchild of engineer Orla Ed Thayer (1920–2009), whose invention (commonly known as the Thayer valve) was first put to the test on a Bach 42B. His revolutionary idea led to many further developments in valve technology.
| F attachment / valve | Bell material / slide | ||
|---|---|---|---|
| Yellow brass / standard | Gold brass / standard | Gold brass / lightweight | |
| Closed / standard | 42B | 42BS | 42BG | LT42BG |
| Open / standard | 42BO | 42BOG | LT42BOG |
| Open / Hagmann | 42A | 42AG | LT42AG |
| Open / axial flow | 42AF | 42AFG | LT42AFG |
The ‘42B’ trombone emerged in the early 1950s as part of Vincent Bach’s expansion into large-bore symphonic tenor production, building on the manufacturer’s established medium-bore models. Featuring a .547-inch bore, 8½-inch one-piece yellow brass bell, and traditional wrap F-attachment, it offered a focussed, projecting orchestral sound distinct from the broader tonal profile of its competitors. While not initiating the large-bore movement, the 42B became a durable standard in American orchestral playing, and continues to influence contemporary Bach trombone design.
Manufacturer’s website: conn-selmer.eu