Classical repertory

In the history of European art music, the common practice period is the era between the formation and the dissolution of the tonal system. Though there are no exact dates for this phenomenon, most features of the common-practice period persisted from the mid to late baroque period, through the Classical, Romantic and Impressionist periods, or roughly from around 1650 to 1900. While certain prevailing patterns and conventions characterize the music of this period, the time period also saw considerable stylistic evolution. Some conventions evolved during this period that were rarely employed at other times during what may still be labeled "common practice" (for example, Sonata Form). Thus, the dates 1650–1900 are necessarily nebulous and arbitrary borders that depend on context. The most important unifying feature through this time period concerns a harmonic language to which modern music theorists can apply Roman numeral analysis.

The harmonic language of this period is known as "common-practice tonality," or sometimes the "tonal system" (though whether tonality implies common-practice idioms is a question of debate). Common-practice tonality represents a union between harmonic function and counterpoint. In other words, individual melodic lines, when taken together, express harmonic unity and goal-oriented progression. In tonal music, each tone in the diatonic scale functions according to its relationship to the Tonic (the fundamental pitch of the scale). While diatonicism forms the basis for the tonal system, the system can withstand considerable chromatic alteration without losing its tonal identity.

Throughout the common-practice period, certain harmonic patterns span styles, composers, regions, and epochs. Johann Sebastian Bach and Richard Strauss, for instance, may both write passages that can be analyzed according to the progression I-II-V-I, despite vast differences in style and context. Such harmonic conventions can be distilled into the familiar chord progressions with which musicians analyze and compose tonal music.

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