- Major = Bright and cheerful – also known as Ionian
- Minor = darker and sadder – also known as Aeolian and Natural Minor
- Mixolydian = major with a hint of minor – often mistakenly referred to as just Major
- Dorian = Minor with a hint of major – often mistakenly referred to as just Minor
Also, a table showing all Major, Minor, Mixolydian and Dorian keys that might be found in folk music of the British Isles, North America and much of Europe:
A quick note here about notes that have two names, or enharmonic equivalents. Every sharp/flat note has two names. For example, the note between F and G can be called F# (F sharp) or Gb (G flat). The reason why one name is used instead of another depends on the musical context.
F# is said to be the enharmonic equivalent of Gb. G# is the enharmonic equivalent on Ab, and so on. Here are all the enharmonic equivalents.
The chart below shows all enharmonic equivalents:
Look at the two examples below, and we’ll see how to work out the key of the music.
First find out the key note…
Assuming that these sections are endings (either of a part or a tune), the two examples above both finish clearly on a G note. The fact that the second example starts on B makes no difference to the key. The last note is a far more reliable guide than the first. So, we can reliably state that these two examples are “in” G something.
Then find out the type of key or mode…
In example 1, you can see that F notes are sharpened, while all the other notes are natural (not sharp or flat). Knowing that the key note is G, now refer to the table on page 45, where you’ll see there are 4 options – G mixolydian, G major, G dorian or G minor. These have no sharps, 1 sharp, 1 flat and 2 flats respectively. The one that corresponds to the example is G major (1 sharp).
Example 2 is made up entirely of natural notes (no sharps or flats) – looking at the chart again, you’ll see that the G key that has all naturals is G mixolydian.
See more on keys here