Left side:

Es1 - e2, four octaves on one side

Inventive spirit knows no bounds. The unisonoric bandonion, designed by Emil Probst from Zurich, is not many tones short of a complete piano keyboard. Not only in the number of buttons (100), but also with over six octaves of chromatic range, it seems to be a record-breaking harmonica instrument.

The keys were arranged in two or three whole tone rows according to the the Janko principle.

Right side: es - e4

The left and right manuals are in opposite pitch directions

This is one of the few bandonion types on which the thumb is used and is also necessary for mastering the system.

The hand straps are correspondingly wider and fit snugly around the wrist.

mechanism of the right manuale

The special feature of the Probst bandonion was that it was only played with pressure wind. After squeezing the bellows together, the player had to moment to 'take air' again.

However, there was no need to operate an air lever because E. Probst had installed valves in the centre frame of the bellows which opened automatically when the bellows were pulled apart so that air could flow in.

mechanism on the right side

Due to the restriction to pressurised wind, this type of bandonion required only half the number of reeds, which is why such a wide range could be realised.

The weight was therefore comparatively low at 4 kg.

Compared to conventional instruments, it is around 9 cm higher, which naturally results in a unique tone colour, especially as its two 8' choirs are tuned by suspension. Both of these were wishes of the buyer, because in concertina and bandonion making was always built to order and not built to stock (Graf, p. 122).

Emil Probst himself played a square instrument with an edge length of 25cm.

Top: The manufacturer of the instrument shown

"Joh. N. Trimmel, VII/3. Burggasse 123, Wien, Austria"

The hand harmonium was also made in Zurich, Schaffhauser Str.151, presumably by Emil Probst himself.

Thanks to the only slightly protruding and lenticular keys, it could be bowed over the keys like a piano (glissando).