Despite my sister's adherence to "old" autoharps, presumably with 15 bars (as opposed to the really old 12s), the Real autoharpers all seem to use the 21s, though seemingly always modified for better chords and chord layout. Unfortunately, there seems to be as many "correct" layouts as there are guys to opine on the topic. Part of the attachment to 21-bar harps is, obviously, more chords, but also the bars are narrower, so the buttons are closer together, and there are three rows of buttons, rather than the 15-bar harp's two.
So, I'm tempted to try a three row layout on my 15-bar Chromaharp (which showed up on Friday) -- though the rationale seems to be Majors in one row, Minors in another, and the 7th in the third. Since I won't have any 7ths, that doesn't necessarily make sense for me.
What worries me now is the matter of playability when it's laid on a table versus held up against the chest. Upright leaves the right (strum) hand in the same place, but reverses the incoming direction of the left. Apparently the idea is to be able to use the fingers and thumb (oops -- didn't think of that!) to chord, with "touch type-ability". I think this means that I'll have the Majors on the top row, so the 1, 4, and 5 are under middle, index and ring finger, and the Minors in the bottom row where my shorter thumb can reach 'em -- and shifted right so the 2m and 6m are *under* the thumb, not necessarily "near" the 1. Or maybe that won't work out 'cuz it throws a lot of the minor chords off the end of the rack...
On further thought, I don't think three rows makes any sense for my scheme, since I won't have any 7ths. The real hang-up now is this left-hand coming in from the top, or bottom, problem. I talked to my sister this morning and she said that she Never plays it laying flat (lap or table). She distains the crossed-over wrists thing you get when it's flat (though that's the way it's pictured in the booklet that came with my ChromAharP). This might explain why the playing position is never mentioned in the FAQ -- it's Presumed Upright by all the Regulars. But it obviously makes a big difference if you're gonna lock your three main fingers on 1, 4, and 5 -- where your thumb ends up (to the left or right of that), is gonna determine where you want to put 2m and 6m. I suppose I'll build it "right" (i.e., meant to be held upright), and my daughters will figure out that it works better that way soon enough. It is, mainly, for them -- but I want it to "bring 'em up right" chord-relationship-wise, so I want to put in the logical chord bars before I let 'em play it much. I can picture them playing along with me on some of my guitar songs, once the requisite chords are available.