Scandalli Air III Bass registers

[Beemer]

I await delivery of a Scandalli Air III piano accordion. Meanwhile I would like to understand the seven bass registrations. Here is a photo of the registration buttons.

 

[Glug]

I'm fairly sure the cassotto is on the treble side.
This looks to be the same model: https://www.accordiongallery.com/Scandalli-Air-III

So the bass registers are interpreted as on https://www.accordionists.info/attachments/scandalli-air-bass-registers-png.6467/

 

[Dingo40]

Beemer,
Can't say I've ever heard of bass-side casotto?

 

[Beemer]

You are probably correct about the two blocks being in a treble tone chamber. However as a beginner the Bass symbols mean nothing to me. Some dots are on a line and others on a space. How am I supposed to interpret this?

 

[Beemer]

Beemer,
Can't say I've ever heard of bass-side casotto?

I'm sure I read a post here that mentioned it. It may have been on a Russian accordion system.

 

[debra]

The bass side of an accordion typically has 5 voices. 4 are represented as dots between the lines and 1 is a dot on the line. The bass then spans 4 octaves. The middle of the 5 voices (the one on the line) sits in between the other "middle" ones but has the octave jump on a different note. This helps to mask where the octave jump is on the other voices, and this works better or worse depending on which register you choose.
There is no such thing as a true bass cassotto on modern accordions, but there are two ways in which the resonance chamber can be enhanced/enlarged: the Winkelbaß puts the lowest octave on an elongated reed block at a 90 degree angle. (So every note has its sound travel to a longer "tube". the Umlenkstimmstock does the same but at a 180 degree angle (thus looking like just a thicker reed block, but in fact having the sound travel through a longer tube that exits in the middle of the thick reed block. You can also tell because the large bass reeds are then mounted upside down on the reed block.