The first thing to remember is that there are in fact two different types of minor mode, and they are identified by the way in which the sixth and seventh notes of the scale are handled.

The Harmonic Minor appears very frequently. In it the third and sixth note is flattened and the seventh note sharpened on both the ascending and descending scales:-

Harmonic Minor Scale ascending

C, D, E flat, F, G, A flat, B natural, C

Harmonic Minor Scale descending

C, B natural, A flat, G, F, E flat, D, C

In the Melodic Minor scale the third is flattened as before, but the rest of the ascending scale is played with the sixth and seventh sharpened, just as in the major scale. The mode's style really changes in the descending scale - the third, sixth and seventh notes of the scale are all flattened.

Melodic Minor Scale ascending

C, D, E flat, F, G, A natural, B natural, C

Harmonic Minor Scale descending

C, B flat, A flat, G, F, E flat, D, C

A minor triad consists of a minor third cord which is followed by a major third:-

C to E flat - minor third

E flat to G - major third

This harmony is used in many different ways in Classical music. Often it is used to form contrasting movements, for example within a sonata some movements may be in its main or related key, and there will be a minor section adding balance. In the Schubert inpromptu sets Opus 90 and 142 we frequently encounter switches between the minor and major which is a very characteristic facet of this composer.

The minor key can be used to suggest all sorts of different colours and moods within the music. The last movement of Beethoven's Pathetique sonata Opus 13 No. 1, for example, is full of pathos and tragedy in complete contrast to the serenity of the first movement which is in the major key. Wagner's funeral march from the opera Seigfried is another example which we normally only get to hear having listened to four hours of musical drama, and so the tension when you do hear it is considerable. Beethoven's Third Piano Concerto in C minor is another example where the main key is in the minor mode, and Beethoven produces a wonderful dialogue within the orchestra at the opening which reflects the sense of the dramatic associated with this mode.

Yet another use for the minor mode is in sets of themes and variations. This particular style of composition is when a composer will take a well known theme and after writing the first version will produce a series of different linked pieces, all variations of the first. Using the minor mode in a theme and variation set is one of the most common variations to be found.

Tchaikovsky produces a superb oriental dance in the second half of his Nutcracker ballet which is another means of utilising the minor mode - the unsettling, fluid harmonies it can produce are a great way of suggesting the exotic.