Being able to determine the key and/or mode of a piece of music has several useful applications. First of all, for writing music, you have to be able to assign a key signature to the music. Secondly, if you know the mode of the piece, it gives you some clues about typical chord progressions and fingering patterns for your button box. Third, it gives a clue (once you have attained familiarity with the modes) about the way the tune will sound, without you having to hear the tune. True, you won't know the melody, but you will be able to predict the "flavor" of the tune (just like we have an idea about what vanilla ice cream tastes like without actually knowing exactly what the brand in question will taste like). Therefore it aids in discussion of music.
Determination of the key is a pretty straightforward process for diatonic tunes. Chromatics can be a little trickier. Boiled down to basics, there are 12 major keys. Some of them have more than 1 name:
- Key of C has no sharps and no flats
- G has F#
- D has F#, C#
- A has F#, C#, G#
- E has F#, C#, G#, D#
- B has F#, C#, G#, D#, A#
- F has Bb
- Bb has Bb, Eb
- Eb has Bb, Eb, Ab
- Ab has Bb, Eb, Ab, Db
- Db has Bb, Eb, Ab, Db, Gb
- Gb has Bb, Eb, Ab, Db, Gb, Cb this is the same key as F# which has F#, C#, G#, D#, A#, E#
So, to determine the key of a piece of music, simply examine the notes which make up the piece and pick the key which contains those notes. For example, if the piece contains the following notes A, B, C#, D, E, F#, G, you know that it is in the key of D because it has F# and C#. It is not in the key of A, because it contains G natural instead of G#. Where you run into a little bit of trouble is when the tune has an accidental chromatic thrown in. Generally speaking this would be a note which sometimes is natural and yet in other parts of the tune, has a sharp or flat sign attached to it. The thing to do in this case is: if it is an isolated occurance, ignore it. If it occurs about half the time, use some deductive reasoning. For example we have a tune which has the following notes A, B, C#, D, E, F, F#, G#. Looking at that, I would call it key of A with an accidental F natural. I wouldn't call it D because the G is always sharp, not natural as it would be in D.
The key gives you some very useful information - like whether a tune is playable on your box, but it leaves a lot of information out. For example, we might determine that a tune is in the key of G, based on the notes in the tune. But the tune might also be in Eminor which shares the same notes, and the same key signature as Gmajor. Well, Eminor is a lot less playable on a G/C box than G major. We also know that Eminor tunes sound a lot different than G major tunes. So if we're looking for a G major tune, we would pass over anything in E minor. But how can you tell if they share the same notes and key signature? That's what I want to discuss next.
E minor is a mode within the key of G. Actually, there are 7 basic modes within the key of G.
- G Major (or Ionian)
- A Dorian
- B Phrygian
- C Lydian
- D Mixolydian
- E Minor (or Aeolian)
- F# Locrian
- G major/ionian - the scale goes G A B C D E F# G or in 1/2 step intervals 2212221. The I chord is GBD or Gmajor, the IV chord is CEG or Cmajor, the V chord is DF#A or Dmajor. Notice how all the 3 chords are major. Obviously G major works well on a D/G box. We have all the chords and all the notes at our fingertips.
- E minor/aeolian - the scale goes E F# G A B C D E or in 1/2 step intervals 2122122. The I chord is EGB or Eminor, the IV chord is ACE or Aminor, the V chord is BDF# or Bminor BUT remember the V chord must always be major to supply the leading tone to the tonic so the V should be BD#F#. D# is not within the scale, so that can present problems on a purely diatonic instrument. Notice how all 3 chords are naturally minor (before we modified the V). E minor also works well on a D/G box, though we have to fudge the Aminor chord in the basses and the Bmajor chord in the treble needs funky fingering.
- A dorian - the scale goes A B C D E F# G A or in 1/2 step intervals 2122212. The I chord is ACE or A minor, the IV chord is DF#A or Dmajor, the V chord wants to be EGB or Eminor but as a V must be EG#B or Emajor. A dorian can work on a D/G if we fake the Aminor and Emajor bass and the Emajor treble chord demands some gymnastics, on a G/C box A dorian is a breeze. Incidentally, many of the tunes that seem to be in Aminor on a G/C box are actually in A dorian and many of the tunes that seem to be in Eminor on a D/G are actually Edorian.
- D mixolydian - the scale goes D E F# G A B C D or in 1/2 step intervals 2212212. The I chord is DF#A or D major, the IV chord is GBD or G major, the V chord wants to be ACE or A minor but again must be AC#E or Amajor. D mixolydian is a breeze on a D/G box.
- B phrygian - the scale goes B C D E F# G A B or in 1/2 step intervals 1222122. The I chord is BDF# or B minor, the IV chord is EGB or E minor, the V chord is F#AC, which is actually an F#diminished chord. In order to make that a major chord we have to go with F#A#C# which requires 2 notes from outside the diatonic scale. This could account for the relative rarity of this mode.
- C lydian - the scale goes C D E F# G A B C or in 1/2 step intervals 2221221. The I chord is CEG or Cmaj, the IV chord is F#AC which is our friend the F#diminished chord (try it if you want a funky sounding chord), and the V chord is GBD or Gmaj. For 2 chord melodies this mode can work fine, especially so on a G/C box, but more complex 3 chord tunes don't work nearly as well.
- F# locrian - the scale goes F# G A B C D E F# or 1221222. The I chord is F#AC or F#diminished, the IV chord is BDF# or Bmin, and the V is....well there is no perfect V, there is only a minor V so .....well just forget it, this mode is of little interest except in experimental music.
For Your Information:
So, how do we tell what mode a piece of music is in? There are a number of factors to consider. Remember how I said that the function of the notes changes from mode to mode? Well, that gives us our first clue. Do you remember how we defined the tonic? "...the tonic is where the melody comes to rest, it resolves melodic tension, usually it is the last note of the melody, the final resting point, the most important note of the scale". So the most important key to determining the mode of a piece lies in determining which of the notes in the melody is the tonic. Usually it is the last note of the melody or phrase, or the root of the final chord if the piece ends in a chord. That's not always true, but almost always. You can check yourself by going over the tune and making sure that phrases are ending on the same tonic, also, usually long drawn out notes or notes that get special emphasis tend to be on the tonic. By listening to the tune, you can determine whether the music seems to resolve in a satisfying way - that confirms that the tune ends on the tonic. If the tune seems to end in an akward or tense place or leaves a feeling of expectation or inconclusivness, it probably ends on a note other than the tonic. If you know the tonic and the notes in the melody (as we discussed earlier regarding keys), you can usually deduce the mode. Not to confuse the issue, but there are many other modes than the 7 "classical" modes I've discussed, but these other modes are not derived directly from the major key, and I will not get into them here. Just be aware that sometimes (rarely) you will encounter a mode which doesn't fit the typical pattern. If you are intrigued by diatonic modes, you can explore them to your heart's content on the bandura side of my website (follow the links) which contains the most comprehensive table of modes to be found on the web AFAIK.
The tonic is the most important clue. Supporting evidence is provided by the chord structure. If you see a progression of Gmaj-Cmaj-D7maj-Gmaj, for example you can be fairly assured that the mode is Gmajor or possibly Gmixolydian, but not likely dorian or minor. Look at the notes of the melody to narrow it down to major or mixolydian. On the other hand, if you see Amin-Dmaj-E7maj you are likely looking at an A dorian tune. And Emin-Amin-B7maj is likely an Emin tune. So to generalize Imaj-IVmaj-V7maj is major or mixolydian most of the time, Imin-IVmaj-V7maj is dorian, and Imin-IVmin-V7maj is minor/aeolian. Sometimes you only have 2 chords, I and V. In that case, if I is minor you are dealing with dorian or aeolian, and if it is major you are dealing with major or mixolydian. You can further narrow it down by examining the tonic and the notes of the melodic scale.
A word of caution which applies to both keys and modes is that some tunes include an excursion or modulation into a different key. An excursion is a brief shift of the key or mode, which usually returns to the starting mode before too long. Sometimes this lasts an entire phrase, sometimes less. A modulation is a more extended shift into a different mode or key, which may or may not return to the original key/mode. The music of eastern europe exhibits this feature quite frequently. A good clue to modal shifts is the chord progression. If you don't have the chords worked out, it is probably good enough to simply check the tonic for each part of the tune to make sure it is the same as the final tonic. Tunes with modulation can be quite fun and interesting to play. A final word to the wise - don't let accidentals trip you up. Treat them as the misfits they are (ignore them for the purposes of analysis).
As stated earlier, the "normal" configuration of a chord is 3 notes (I, III, V) or 4 notes (I, III, V, VII). There are other chords besides. Chords can have as many notes as you like in them. Besides that, they don't necessarily have to be major chords or minor chords. Diminished and augmented are other possibilities. We will not get too deep into the intricacies of chords. There are jazz tutorials for such things and I'm not much of a jazz afficianado. I will just mention some basics to get you thinking.
Triads can be major, minor, augmented or diminished. We have looked at major and minor chords at length, but we haven't really talked about augmented and diminished. Remember that a minor 3rd consists of 3 half steps, whereas a major 3rd consists of 4 half steps. Recall also, that that a minor triad consists of a minor 3rd followed by a major 3rd e.g. CEbG. A major triad is the opposite with a major 3rd followed by a minor 3rd e.g. CEG. In either case, the triad spans a total of 7 half steps e.g. C-G is 7 half steps or a perfect 5th. If we have a minor 3rd followed by a minor 3rd, we have a diminished chord, which spans only 6 half steps e.g. CEbGb. If we have a major 3rd followed by a major 3rd, we have an augmented triad which spans 8 half steps e.g. CEG#. These triads sound abnormal and odd to most ears. They are mainly avoided in folk music, but have found some use in other musics and can be used to spice up some folk tunes. They also appear in some of the less common classical modes.
The 6th chord (I, III, V, VI) is not too uncommon. There are 3 types of 7th chord - major 7th, minor 7th, and dominant 7th. Remember, the dominant 7th is the one that gets used in the dominant V function - in it the 7th is lowered 1/2 step to keep it within the scale. If you are using a 7th chord in a position other than the V, you will use a major or minor 7th depending on the chord and the scale. For example in the key of C, C7 would consist of CEGB. Since B is just 1/2 step below C, it is considered a major 7th chord or C7. In the key of C, Dmin7min would consist of DFAC. Here, since C is a whole step below D it is considered a minor 7th chord.
A C13 chord has 7 notes in it - I III V VII IX XI XII or C E G B D F A (it spans more than one octave). Look at that again, isn't it the same as saying C D E F G A B? Yes, it is. Jazz players tell me that its all a matter of what you're used to. The way you get used to it is to play a C7 chord then play D F or A against it or play C scales against it, then slowly as you get used to it, play all of them against C7, or play a C7 and a Dmin simultaneously. Soon it will begin to sound normal and you will find that you can play any melody in C major against a droning C7 chord. Same principals apply to 9th and 11th chords. Sometimes, due to a shortage of fingers (which are in limited supply) jazz musicians will leave out the 7th, 9th, or 11th notes of the chords in a 13th chord. Those notes are implied. You can do the same on a button box.
On a D/G box you can play a full D13 on the bass by simultaneously playing Emin, Dmaj, and Cmaj or C fundamental, or by playing Dmaj, Cmaj, and B fundamental depending on whether you want it on the push or the pull (yes, that's right, you can play a D13 bass on the push AND pull on a 2 row diatonic). By leaving the B off, you have a D11. You can get an Emin7 by playing Emin and Dfun. You can get A9min7 by playing Amaj and Emin and A13min7 by playing Amaj Emin and Dmaj. Gmaj + Dmaj gives you GBDF#A which is G9. Add a Cfun and you get G11 or add a Cmaj and you get G13. Cmaj + Bfun gives you C E G B or C7. Cmaj +Gmaj gives C E G B D or C9. These are just some of the possibilities. You can also create chords by combining the left and right hands. The possibilities there are vitually endless. Again lots of chords and the notes that go with them are found in the bandura section of my website, along with the corresponding modes.
