I need a Bm chord

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I need a Bm chord

Postby Bob Lewis » Wed Jun 18, 2008 7:53 am

-----Original Message-----

I have an OS-21C, 21 chords. I have all the 7's on the top row, majors and one Dmin on the second row a Gmin, Dmin, Amin, Emin, Bb7, Cmin, and Bb7sev on the bottom row. Which one would I toss to put a Bmin on the bottom row. I am thinking the Bb7. Any suggestions?


This is a FAQ addressed at


The third one down, "Lewis Bluegrass", identical to Cathy Britell's recommendation on her site, shows use of standard keys, except that Ab, Cm, and Bb7 are dropped in favor of adding E, Bm, and F#m. The E chord is not necessarily essential but it satisfies the logic of the new approach to the layout. You drop a flat key (Eb) on one end and add a sharp key (E) on the opposite end. When you add a sharp key, the other keys shift to the left and take on more or less favorable felt damping positions over the strings. What was a CGD 'harp is now a GDA 'harp. The prime keys have changed.

I understand and respect other approaches well enough, but the chord selection and layout that I chose to use on my standard tuned Bb/F/C/G/D/A chromatic and recommend to others is as follows:

P-treble side
N-bass side

The diminished 7ths are included only on the condition that they would be in reasonable tuning. I use 1/6 comma meantone, but Charles own special tuning should be acceptable, certainly better than "standard". Regardless of tuning, they could also be useful to help pick out single notes rather then be played as out-of-tune chords or to present a harmony that players of other instruments in a group might not appreciate.

B7 is dropped because its D# string tuning conflicts with the tuning needed as Eb. If believing one needs a B7, then the key of Bb gets lost, sacrificing the Eb chord and trading Eb tuning for D# tuning.

In the short term, adding only a Bm and not addressing the dim7 question, the layout with mostly standard chords would look like this:


That would mean you dropped B7 and added Bm.

In order to address other questions, other quandaries that the chromatic configuration presents, I use multiple instruments set up in different ways, favoring different keys. Just as the key of C sounds the most "at home" on a standard autoharp, and evidenced by a technician finding the preponderance of instruments come in showing the most wear on the C chord button, the autoharp can be modified to specialize in another key plus almost as good on a neighboring key group to each side of the prime chord button group. Standard, as recommended to you above, is the key grouping, CGD. It will always be the chord group within the first 15 bars on the right. Anything else to the left will have harmonics issues bad enough for the player to try to avoid them. Those secondary keys/chords get used only of necessity, the sound of them only marginally considered real music.

An example of customizing on a second instrument would be to change the above layout from CGD to GDA as follows:


This instrument could play in FCGDAE instead of BbFCGDA. C will no longer be a great key because its bar grouping sits too far to the left, pretty much spoiling the F chord.

So, when having only one instrument, changes should be well considered. You will make it so that you cannot play some music. You only change the percentages, so if most of what you encounter is in G, D, or A, your instrument should be setup to favor those keys. We know the keys on the instrument are never all equal. A purist uses an instrument with only 5-7 bars, so obviously there are compromises involved with a 21 bar instrument. What I often find is that players of the 21 bar tend to use only 5-7 bars, when given a choice. They know where the sweet spot is on their instrument, and they know which keys to avoid. One can know something sounds bad without necessarily understanding why.
Bob Lewis
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