Most traditional music, and folk music in general, is not chromatic in nature, it is what we call diatonic....in other words it uses only 7 of the 12 divisions of the octave. This is the type of music for which the button box was concieved. The most common diatonic scale is the Major scale. It corresponds to the white keys on a piano.
Now the Major scale does not use just any 7 notes out of the octave. It uses 7 very specific notes. We generally speak of these notes by specifying the intervals between them. So if we number the 7 notes from 1 to 7, and knowing that 2 half steps equals a whole step, the major scale looks like this: 1w2w3h4w5w6w7h (where w means whole, and h means half) After the 7th note, the scale starts over with the 1st note. In condensed form, you could represent the Major scale thusly: wwhwwwh, remembering that there is a note implied between each letter. Sometimes, rather than speaking of wholes and halfs, you will hear people speaking of 2s and 1s. This is very easy if you just remember that w=2 half steps, and h=1 half step. I actually prefer this method (mainly because when you start talking about pentatonic scales and other less common scales, sometimes you have 3 or 4 half steps, and those are easier to write and understand as numbers rather than letters or fractions). So in my preferred notation the Major scale looks like 2212221. Logically, if you add up those numbers, you should get 12. If you don't, its a sure sign that something went wrong.
The next most common scale in western music is the Minor scale. The Minor scale uses the same progression of intervals as the Major scale, the only differance is that the minor scale starts on the note that would be the 6th note of the Major scale. This is how the Major scale relates to its "relative Minor".
So taking what we know about the Major scale, and modifying it, we can determine that starting on the 6th note, and wrapping back to the 1st note after the 7th, the sequence looks like this:
6w7h1w2w3h4w5w Now, the 6th note of the Major scale is the first note of the Minor scale, so we can renumber as follows:
1w2h3w4w5h6w7w or in condensed form: whwwhww In numerical notation 2122122. Again, a quick check shows that the numbers add up to 12.
So, lets apply this information. We know the 12 notes in an octave, and we know the intervals for the Major and Minor scales. so lets construct a C Major scale. The scale will start on C (it always starts on the note it is named after). We see from above that the next note will be 2 half steps above it...that would be D. The next will be 2 half steps above D, which we can see is E. Now we add only 1 half step to E to get F. Then 2 half steps gets us to G, 2 more to A, and 2 more to get us to B. These are the notes of the C Major scale: C, D, E, F, G, A, B. Normally when playing a scale, our ears like us to finish on the root or tonic of the scale, in this case C, so C,D,E,F,G,A,B,C would be a fine way to write or play this scale.
We can do likewise with the Minor scale. Lets stick with C, and construct C Minor. Again, start with C and add 2 half steps to get D. Now add only 1 half step, as shown in our interval map above, to get D# (also known as Eb). Then add 2 half steps to get F, 2 more to get G, 1 more to get G# (also known as Ab), 2 more half steps get you to A# (also known as Bb). So the notes in the C Minor scale are C, D, Eb, F, G, Ab, Bb. I chose to use the alternate names of Eb, Ab, Bb because it is conventional to use all the letters in the scale, and otherwise E and B would not have been present.
The usefulness of this information may not be immediately apparent, but it will become clearer, the more you get into music. One use is that you now have the basis to figure out the 3 common chords that go with any Major or Minor scale. The details of how to do that will be included in the section on constructing chords.
Every triad consists of a root, third, and fifth. The root is the fundamental note of the chord. It is the note which the chord is named after. So, for example, in a C chord, the root note is C. From our work in the last section, you can now figure out what the 3rd and 5th notes of the C Major scale are. E is the 3rd and G is the 5th. Therefore a C Major chord consists of C,E,G.
Now lets figure out the C Minor chord. Again, the root is C. From our work with the Minor scale above, we know that the 3rd note is Eb and the 5th note is G. So the C Minor chord is made up of C, Eb, G. Easy huh?
Now I would like for you to notice something. The only difference between the C Major chord and the C Minor chord is one note, the 3rd interval. If the 3rd interval is Major, the chord sounds Major, if the 3rd interval is Minor, the chord sounds Minor. If you leave out the 3rd interval, it will sound neither major nor minor, but neutral. Technically it is no longer a triad, it is a diad. Some button box players use this bit of information to expand their ability to harmonize the bass hand with the treble. They purposely mute or remove the 3rds from the bass chords to allow themselves to play neutral diads. It is a trade-off... expanded ability to harmonize, but at the expense of thin, wishy-washy sounding bass "chords".
And you thought none of this was practical!