Tonality
Most Western music from about 1600 onwards is based in a major or minor key. This system of tonality was used by all the great composers up to the 20th century and in popular music and most folk music. Listening to a symphony by Beethoven is like going on a journey through various key areas, always returning to the original tonic at the end. In some cases, such as Beethoven’s Fifth Symphony, it may start in the minor and finish in the major. This is because minor keys can sound disturbed, full of tension, but major keys sound happier and more relaxed.