The portative organ that we looked at last week was a small, portable organ, played by a single person. It’s close relative, the positive organ was larger and took two people to operate. It was usually set upon a table for playing.
Generally it had twice as many pipes as the portative organ and a larger keyboard. Whereas the portative organ had one bellows, the positive organ had two. This meant that the player could use two hands on the keyboard, leaving him no hands free to pump the air into the pipes. I’m not entirely sure what’s going on with the bellows in the picture at the top of the post, but I think the reality must have resembled what you’ll see in the video, rather than the weird, man-size bellows connected to the pipes by a tube that looks like it could eat the player for breakfast and hardly notice.
We noticed last week that there was a lot of co-ordination required between the hand playing the keys and the hand pumping the bellows on the portative organ. That wasn’t really possible when someone else was doing the pumping, even more so when they couldn’t see the hands of the player, so it made sense to have two bellows ensuring that the organ never ran out of air.
In this video you can see that dealing with the bellows is not as easy as you might think. The chap managing them has to make sure that there is a constant flow of air to the pipes, which means co-ordinating the bellows. He doesn’t have to push them down, just lift them up and he lifts one while the other is descending.
A History of Western Music by J. Peter Burkholder, Donald Jay Grout and Claude V. Palisca