Art Reblitz wrote in MMD 981031:

> The B.A.B. system uses two single-tap beaters with very powerful
> pneumatics, played from two separate holes in the roll, as in Gavioli
> and most other European fairground organs.  With this system, either
> hole in the tracker bar produces a loud clear single tap; for a
> continuous drum roll, the roll alternates the two beaters rapidly.

It may be interesting, though, that the largest style of Ruth factory
[organ], the style 39 (quite famous because of the unique musical
repertoire), has the same kind of drum beaters as the Wurlitzer!  Only
one hole is playing both drumsticks alternately.

Despite an optimal regulation in museum circumstances, those drum
beaters never work properly.  Moreover, two spaces away on the
trackerbar, there is an unused hole.  So much for Ruth!

Hans van Oost, KDV, Netherlands