Concertina vs accordion reeds in General Concertina Discussion Posted April 30, 2020 · Edited April 30, 2020 by Łukasz Martynowicz 9 hours ago, Little John said: An illustration might help. There are three natural notes ("white" notes on a piano) in each row (or arc) and there are three corresponding chord shapes. In the attached chart: Top left shows how D minor, G major and C major have the same shape, based on the fourth column from the left. Bottom left shows how moving your finger to the outer column* of accidentals ("black" notes) changes major to minor and vice versa for the same three chords. Top right show how the three major chords in the key of F have similar shapes, based on the second column from the left. Bottom right shows that a few variations are possible. This is my favourite form of C major. Chords based on the middle column follow similar patterns. So pretty well all chords follow one of three basic patterns, the variations being that the outer columns are used when "black" notes are required. LJ * Or using your little finger, as I do for that column. Crane chord shapes.pdf 65.5 kB · 17 downloads Thanks, that was informative. From a perspective of a Hayden player I would say that Crane system is half way there: it is fairly logical within an octave and chords aren’t „all over the place”. It has some resemblance to 3-row variants of accordion B- and C-systems in that you have different but limited shapes of chords depending on row of the root note. On the Crane however it all goes out the window when you go up an octave - same chord octave higher is fingered entirely differently. @RAc while it is true what you say about „music theory coming alive” in this example, it is also true that in order to construct chords on a Crane one has to already know music theory and how to construct every chord he wishes to play. That is not the case on isomorphic keyboards: the layout itself teaches you theory! (That of course includes the simplest isomorphic layout of them all - bleached and leveled, entirely linear version of piano keyboard:) )That is what I find most usefull about them - all you need to know to play a chord is it’s universal shape and root note. You get all other information directly from your fingers.