In brief, nothing.It's not often that I am TOTALLY lost when trying to understand a point about concertina systems. A Google search for Pitt-Taylor revealed an article by Brian Hayden (perhaps I should ask him to comment), but I have extracted the following:
The Pitt-Taylor, e.g., has made me aware of some previously unnoticed advantages to cross-row playing on the anglo.What I'm wondering, is what this system taught you, in terms of cross-row playing on the Anglo?
Some people see the "square form" of keyboard as different from the ones that have set intervals in triangles, however I see this as a special case with right angled triangles, where one set of intervals is about to form into another. Take for example the Pitt-Taylor 1922 Pat.No. 208274 keyboard. with semitones along the rows of notes and half octaves above them, i.e. a rows of notes:
F F# G G# A Bb
B C C# D Eb E
Sorry that my earlier comment, using that as an instance rather than the purpose of the post, wasn't filled out with full background. Pitt-Taylor designed several different keyboard layouts, and mine is not the 1922 layout, but the much different 1924 one. (More can be found in this article by Brian, pp.15-17, with the diagram of my instrument on p.17.) It bears some resemblance to the Maccann, but with significant differences.
What I learned: Some keyboard are designed to have notes that are adjacent musically also adjacent on the keyboard. There are many ways to interpret this, as chromatic adjacency is not the same as diatonic adjancency. An alternative is to have musically adjacent notes deliberately spaced apart, so that playing a scale involves some sort of alternating pattern. On an English, the diatonic scale alternates ends of the instrument. On a Maccann it's an (imperfect) left-right alternation from side to side of the end. What my Pitt-Taylor adds, though apparently not as a primary design principle, is some forward-back alternation (or up-down, as the keyboard is normally pictured on a sheet of paper).
Where I can use it, I find this aids the comfort and smoothness of playing. You might get a similar effect on a Maccann not in playing scales, but in playing certain chord patterns... e.g., the sequence G-D-B-D or F-C-A-C. (C-G-E-G has the vertical, but not enough of the horzontal, IMO.)
This led me to realize why on the (C/G) anglo I sometimes use the two "identical" G/A buttons alternately, i.e., G in the one row followed by A in the other or vice versa. A couple of particular 3-note patterns would be G(G)-A(C )-B(G) and A(G)-G(C )-F#(G). The push-pull pattern is the same, but reaching in alternate directions makes it easier to adjust my hand position to accomodate to whatever notes come before and after. E.g., if I started that second sequence in the left hand with my ring finger and kept it all in the G row, then I would have to play the F# with my little finger (or "jump" a finger). Reaching up and over to the C row let's me easily shift the ring finger down to play the F#, which I might want to do if I want to use more of the lower buttons (especially likely if I have a pull A rather than a duplicate D at the bottom of the G row).
I think that such positional alternation can be a significant advantage in playing, when it can be used, and I think that the foward-back form of alternation has potential advantages which have generally been overlooked.
[Edited just to add a word missing from my intro.]
Edited by JimLucas, 30 August 2007 - 03:18 AM.