Variations on the 3 Row Diatonic Keyboard
Standard 3 row
This is a long time standard setup with 31 treble and 12 bass. Each row follows the same diatonic pattern and each row is seperated by a 5th (or 4th) from its neighbor. This turns out to be very convenient for players of standard 2 row boxes, because the cross fingering can be transplanted directly to the 3 row. Of course, with 3 rows, additional opportunities for cross row playing also exist. This setup is most flexible in the key of C, followed by F, then G. Bb runs a distant fourth, followed by D. However, the best key for Mixolydian tunes is F (Cmix). In this setup, the goal is not to be able to play in any key, but only play well in specific keys. In spite of that, it is theoretically possible to play in all keys in at least 1 octave. The instrument is completely chromatic through 1 octave on the pull. In addition, the keys of C, G, and D can be played totally on the push or pull, and all other keys can be played completely on the pull if desired. The 12 basses are set up to support the keys of G, C, and F, and the inclusion of Dm and Am give increased possibilities for playing in aeolian and dorian modes in 2 key signatures with full bass support. Because 5 of the treble notes have exact duplicates on other rows, this system is not the most efficient 3 row setup, it is however, probably the easiest to learn .
Hohner's Club 33
With 33 treble and 12 bass, the top of the line 3 row layout from Hohner is both bigger and more powerful than the Standard 3 row. It holds to the same layout principals as the smaller 30 button Club model, but expands on that idea, and brings the bass into better balance with the treble. As in most G/C instruments, the most versatile keys are C, then G, F, and finally D. However, D is relatively weak compared to the other 3. Like it's smaller cousin, this Club model is chromatic through 1 octave on the pull. It can also play in C and F completely on the push or pull. The basses are a significant improvement over the smaller model. The extra 4 basses can be considered accidentals, since they don't really pertain to the key of C or G. As such, they won't get as much use as they might otherwise, but at least they are available. This layout benefits greatly from the addition of a stop to remove the 3rds from the bass chords. Although the basses are improved over the smaller Club, the non-standard layout of the treble is not, requiring a re-learning of fingerings. I do not know of any professional diatonic players currently recording with the Club system.
Hohner Club G/C
Irish Hybrid B/C/F
Here is an interesting development in 3 row boxes which is getting to be more and more popular. Take an Irish B/C box, which is fully chromatic in its own right, and mate it to a C/F which takes fewer bellows reversals, and can treble chord and bass accompany well, and you come out with a B/C/F box. Aside from it's inherent capabilities as a unified instrument in it's own right, it can be played in B/C Irish style or C/F European style, thus covering a broad range of musical tastes. In my estimation, if not for the split personality of the system, it would likely not be very popular. Although it is more powerful than either a B/C or C/F alone, it is not as powerful as the other 3 row systems, not even the G/C/F. It has 4 notes which are exact duplications between the rows (compare that with 2 for Heim). It is not fully chromatic on the pull, but with 4 bellows reversals it becomes chromatic in 3 octaves. C and F are the only keys which can be played completely on the pull. None can be played completely on the push. A push D and pull C in each octave would help it cosiderably. Overall, the system plays best in F, then C, but strangely, the key of G (Am) is the best aeolian mode on the instrument and Bb (Fmix) is the best mixolydian mode on the instrument. The bulk of the remaining keys can play, but weakly (even the key of B). I don't know of a standard bass system for the layout, but the few that I've seen use a 12 bass system lifted directly from the G/C/F. Unfortunately, this doesn't match up very well with the treble. The system could benefit from a customised bass layout, but that would not fully compensate for all the duplications and lack of reversals found in the treble.
Irish Hybrid B/C/F
Francois Heim's layout is derived from Jean-Michel Corgeron's, differing from it in only one note - a push A on the third row. While the same size as the Club model we just examined, it is more versatile, and more focused on the home keys. In particular, Heim's layout really strengthens the A aeolian mode. Which makes some sense, since Heim specializes in modal Eastern European tunes (which rely heavily on the aeolian) on the button box. The system is fully chromatic through 2 octaves, though chromatic scales require a bellows reversal. On the other hand, the keys of G and D can be played completely on the pull through 3 octaves, while the C and F scales can be pulled through 2 octaves. The key of G is strongest in Major and Dorian tunes, while the key of C is better for Minor and Mixolydian tunes. In fact, because of the focused nature of this layout, it delivers the strongest performance from the keys of G and C, and their associated modes, of any other system analyzed on this site. Unlike some of the other instruments we have looked at, the key of D is superior to F in this layout. The extended bass system is similar to most of the others on this page, consisting mainly of accidentals, and it benefits greatly from a 3rd stop. It would be interesting to tweak the bass layout to make it more focused on G and C in keeping with the treble, and see whether this results in any improvement to an already excellent layout.
Francois Heim's G/C
If Heim's layout is derived from Corgeron's, Corgeron's is derived from Bruno LeTron's. Corgeron's departs from LeTron only in the first button of the outside and middle rows, and in the 4 extra basses, which though they play the same notes, are reversed. Corgeron's system is not as focused as Heim's (but more focused than LeTron's), performing not quite as well in the home keys, but just a bit better in most of the others. The push Bb on the inside row gives the key of F a boost and makes F almost as versatile as D. Like Heim's, the keys of G and D can be played completely on the pull through 3 octaves, while the C and F scales can be pulled through 2 octaves. The bass system is identical to Heim's.
Jean-Michel Corgeron's G/C
At 30 treble and 12 bass, this is one of the smaller 3 row layouts, and although not quite as versatile as the larger Heim and Corgeron layouts, it packs quite a bit of muscle for its size. It is a more broad-based system, lacking the focus of either Heim or Corgeron. Interestingly, G is a stronger key than C here, and although D is better than F as in some of the others, the key of E major is surprisingly accessible, even moreso than F major, with full bass support! It is fully chromatic through 2 octaves with bellows reversal required. The keys of G, C, D, F, and Bb can all be played on the pull only through 2 octaves. The outside and middle rows are very uniformly diatonic, continuing the diatonic pattern throughout. The inside row also has a uniform pattern, being mostly accidentals with reversals for F# and G, and curiously, D#, an accidental often neglected in other layouts. The bass system differs from many of the others in that it offers a unisonorous B. The D# bass is included as a 5th reversal for the A# bass, but is otherwise not very useful. Another quirk of the bass system is that the pull A is major instead of minor. This seems to indicate that a 3rd stop is highly recommended and often used, or that the system is intended to omit the 3rds from the bass altogether as a matter of construction (as suggested by Pignol/Milleret).
Serge Desaunay's G/C
This is another of the smaller but potent systems, weighing in at 30 treble and 12 bass. It is even more broadbased in approach than Desaunay's and an even better performer if the repertoire is not home-key-centric. In this system, C is the strongest key followed by G, F, then D. The outside and middle rows are quite standard, but coupled with the inside row, the instrument becomes completely chromatic on the pull through 1 octave. In addition G, C, D, F, and A can be played completely on the pull through 2 octaves. The extra basses are accidental based, and like many of the others, benefit from a 3rd stop.
Erik Greve's G/C
Bruno Le Tron's
Bruno Le Tron's layout, one of the "big boys", is probably the least G/C centric of the bunch, and a stellar performer for the musician who wants to wander through the circle of keys (as LeTron does). Like Desaunay's it is somewhat of a quirky layout. Yes, it still plays best in C, followed by G, but then things get wierd. Eb plays easier than F, and Bb and even Ab play just about as easily as F! Furthermore, all of the above play more easily than D. Unlike Corgeron's or Heim's, LeTron's is completely chromatic on the pull through 1 octave. The reversed extra basses seem to match the treble better than the same basses in Corgeron's layout, and again, they are greatly enhanced by a 3rd stop.
Bruno Le Tron's G/C
French Accordeon Diatonique
This layout is very similar to Corgeron's, differing only in the first button on the outside row, and it incorporates the bass system from LeTron's layout. These are very minor changes, tweaks really, but they do slightly improve the performance of the system. All around, this is probably the best performer of the bunch (all keys taken as a whole). It retains much of the versatility of LeTron while improving performance in G and C (though not to the level of Corgeron). In this system, D performs better than F, but as in LeTron's Eb also performs better than F. Like Corgeron's it is not fully chromatic on the pull, but requires a bellows reversal. However, about half of the keys can be played exclusively on the pull through 2 octaves. Again, basses are helped quite a bit by a 3rd stop.
French Accordeon Diatonique G/C