Atzarin bandonion button arc improvements

The button spacing, size and stepping of the Stage 2 prototype were all redesigned to maximise comfort and facilitate playing technique, particularly the use of the thumb on the first and second rows. In terms of appearance, the new, stepped keyboard of larger sized buttons is a fairly radical departure from both traditional bandoneon and B or C system bandonion.

Spacing - 2mm was added to the distance between rows giving 17mm from button centre to button centre along first diagonals and 16mm along second diagonals. Another millimetre was added to the spacing between buttons along the same row giving 15.5mm from button centre to button centre along the first row, closest to the hand rail, 16.5 mm along the second or central row, and 17.5 mm along the third row.

Size - The new spacing allows slightly bigger buttons to be used. Larger, rounded top buttons, as used on the bass side of some diatonic accordions, are more comfortable, particularly for the thumb and may allow glissando to some extent. Whilst traditional bandoneon buttons measure 10.5mm in diametre, the proposed button size for the Atzarin bandonion is 11.8mm.

Stepping - On the Stage 2 prototype, as on a traditional bandoneon, the buttons stood about 1 millimetre higher on each row as they move out from the hand rail. Despite the "angle of attack" of the fingers, this minimal incline was insufficient to enable precise use of the thumb on the second row.

Even using the middle finger to press a button on the first row whilst pressing some buttons on the third row with the index and ring fingers, as when playing a minor triad chord, was not entirely satifactory as the middle finger would curl too far forward onto the nail with a risk of slipping. Stepping the keyboard reduces excessive finger curl in this situation and enables full use of the thumb on all rows.

The proposed step height from row to row for the Atzarin bandonion is 4mm.