The standard Stradella bass system on the accordion only provides four chord types: Major, minor, 7-th and diminished. It's possible to play other chords by using combinations of chords (two ore more chord buttons pressed at one time). Look at this example:
Let's look at the complete Stradella bass diagram
Pressing both CM and Em at the same time gives you the four notes that are required in the Cmaj7 chord.
Listen: chcomb.wav (105k - 16 bit 16 kHz mono), chcomb.au (26k - 8 bit 8 kHz mono)
This is a rather complex topic and it may often be easier to play the chords with the right hand instead. Stephen Keen, firstname.lastname@example.org has written the following article (I have changed/corrected the text slightly and added some pictures). See also Stephens klezmer music website.
The last part of the article is a list of the most commonly used chords in the key of C. You may use this list for chord combination in other keys if you transpose the chords. Use the Stradella bass diagram for this. An example: Gmaj7 = GM + Bm.
For help on finding the notes of a certain chord, try the chord finder at chord house.
The following article was written by Stephen Keen:
Here is a compilation of chord and bass combinations for the left hand buttons. Some of the combinations are difficult to reach and will require the creative use of fingerings and counterbass buttons. Some are downright painful. Some of the combinations are slightly strange sounding but might be appropriate in jazz or contemporary settings. Many combinations, however, generate ordinary and commonly used chords that could be very useful in many styles of music. There is a fair amount of redundancy, but I included all combinations in order to provide alternative positions that may be easier or more appropriate in the context of the music. The most useful combinations, in my opinion, are bolded. Extremely dissonant combinations were omitted reluctantly, for there are many more interesting sounds that defy names. I leave those to the more adventurous.
I begin with some general comments about chord nomenclature and peculiarities of the accordion for those who might be a bit rusty on theory. This is followed by 7 sections of button combinations beginning with combinations of 1 bass note with 1 chord. I omit the obvious combination such as C bass + C major = C major as well as most of the combinations where the bass note is simply one tone of the chord such as C bass + F maj = F/C or C bass + Ab maj = Ab/C. All examples are given in the key of C or with C as the bass note or the root. Of course, eleven other chords are possible by just transposing the example. Each section deals with a combination of the C bass button with one of the chords in the C row ( major, minor, dominant 7th and diminished) PLUS one additional triad. Another section deals with combinations of the C bass and TWO triads not found in the C-row while the next deals with combinations of chords from the C-row only with nearby counterbass buttons. Lastly, most of the commonly used chords in the key of C are summarized with the combinations that can be used to create them - a resorting of the material already described with a bit of new material as well.
I hope that some of you squeezeboxers find this useful. Many of these combination chords really sound wonderful to my ears and it is my hope that some of you will incorporate some of these sounds into your music. Please send me a tape if you do - I would love to hear.
First, let's clarify some standard chord nomenclature so that we're all speaking the same language. I'll jump right to the most ambiguous standard notation on the assumption that accordionists already understand Maj, Min, Dominant 7th and Dim7th chords. Examples are given in the key of C and the numbers represent degrees of the C major scale:
The accordion creates triads (3 part chords) for all of the Maj, Min, 7th, and Dim 7 chord buttons (some accordions may not, but all in my experience do) This is curious because Dominant 7th chords and Diminished chords are, in theory, 4 part chords. This makes chord combining on the accordion different from chord combining on paper or on the piano. We must recognize that Dominant 7th chords and Diminished 7th are implied by the root, third and 7th only (NO FIFTH). This actually is very fortuitous.
It is possible, for example, to play a dominant 7th chord using the dim 7th button because of the missing 5th. On the accordion Cdim7/F sounds virtually identical to F7/F. Try it. The missing 5th also allows us to create a true augmented chord (+5) by playing a dominant 7 chord and filling in the augmented 5th in the right hand. This will not work against a Major triad since that is NOT missing the fifth. Another way to produce and Augmented chord would be to combine a C7 with an E7 (both of which are missing 5ths). The combination creates a true augmented chord (with a 7th and a 9th, a C9aug chord).
The minor 6th chord is almost always better described as an inversion of a min7(b5) chord. For example, Cm6 is equivalent to Am7(b5). Which to call it is dependent on the context, but the context usually points to the latter. Curiously, C bass + Cdim7 yields a Cm6 chord on the accordion because of the missing 5th ( C, Eb, A ). The 5th is understood to be G since it is not there and the chord is heard as Cm6 or Am7(b5)/C. Another more useful way to play this chord is to play Cm/A using the A counterbass which is easily reached. A third way to get a full m6 chord is to play Cbass + Cm + Cdim7 which sounds all 4 notes of the chord. (Remember that Cdim exists on the accordion without a 5th) . To get all four notes of a diminished 7th chord to sound, combine two diminished 7th chords a minor third apart (i.e. 3 buttons away in either direction).
The nearest we can get to a sus chord (suspended 4th, that is, the 3rd raised a 1/2 step) is one of the following combinations: Bb/C Gm7/C Gm9/C These are all very useful chords - find them in the listings below to see how to combine buttons to create the chords.
Well, onward to the button combinations. I think that about covers the preliminary theory review. Please Email with questions if you are confused. Remember , these combinations only work on the accordion -- they will not produce the same chord on the piano. All of the combinations are actually possible to play with some creative fingering, though, I must admit, some are pretty nearly impossible, but I included them anyway.
STEVE KEEN (in sunny Salt Lake City)
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