Yes I know the mercinatomusicale website. A few months ago I had a look at the 2 bassi, 4 bassi and 8 bassi organetti.
They have quite a range of these dubotte and organetti in Italy.
I prefer the unisonoric models Michel Montanaro and Lasse Pihlajamaa are playing in the videos.
I saw the Duo Montanaro in a live gig some months ago in Belgium.
The Pihlajamaa little chromatic button accordion (4 x 3 = 12 basses, or 5 x 3 = 15 basses ? I cant really tell in the video, unclear) seems to be having 2 full octaves on the melody side. With that you can do quite a lot. And if his little box has major and minor chords, then it becomes really interesting.
The Busato firm in France in the 1950s already produced a prototype:
Modèle réduit de latelier BUSATO, Paris (circa 1950)
(un des plus petits accordéons du monde connu)
the photo is here:
http://www.boite-accordeon.com/galerie5.html
Joseph Fiers from Bruges, Belgian accordionist, also had one little box made for him:
http://www.erfgoedcelbrugge.be/product.php?lang=NL&prodid=115&catid=44&itemno=&pos=8
(in the photo its the little one resting on the chair)
The Big Fiers is actually in a Holland accordion museum, you can see the pics here:
http://www.accordeonmuseum.com/am/museum/het-museum/
Dutch TV show with item with the biggest accordion:
There are more than 1 biggest accordion, I suppose every accordion museu has got his records.
Im more interested in the smallest practical accordion, for busking outdoors (light weight !)...
I would very much like to know the exact weight in kg of the little Fiers, the little Pihlajamma cba and the Montanaro mini piano accordion...
Someone an idea?