There are seven modes of the major scale, and they are identified as:

* Ionian

* Dorian

* Phrygian

* Lydian

* Mixolydian

* Aeolian

* Locrian

A variation of a scale is usually known as a mode. Every scale whether it be higher-ranking, or minor, is characterized by a peculiar pattern of tones and semi-tones. For instance, according to our old friend the higher-ranking scale is built from the formula 2 2 1 2 2 2 1, which depicts the gaps between each of the 8 notes.

A mode of a scale is just a magnetic variation of that certain scale in which the pattern of Tones and Semitones in its formula is adjusted. For instance, a scale can be built like this: 2 1 2 2 2 1 1 (this in reality presents us the Dorian Mode). The particular rules for the creation of the modes of a scale'll be discussed later, but the description mentioned above is the gist of what modes are.

What benefit they render?

The modes can be employed to change the whole feel of a song just like we utilize the higher-ranking and minor scales to create extraordinary effects within a song. Some modes are very somewhat unlike to scales we are already familiar with, others are quite strange sounding, but all can be employed to remarkable effect to change the underlying way a song sounds, simply by using notes from a particular mode to compose your melodic phrase from. A song composed by applying the Phrygian, or Dorian modes will sound very different. Each mode lends a unique character to the song and has a characteristic feel.

Now, the great news is that you have by all odds used a couple of modes already, and there is a very great chance that you have employed a few others without actually thinking about it. That's the special thing about musical theory - a good percentage of it is devoted to describing stuff that you actually experienced already.