The word trope or tropus may refer to a variety of different concepts in medieval, 20th-, and 21st-century music.
The term trope derives from the Greek (tropos), "a turn, a change", related to the root of the verb (trepein), "to turn, to direct, to alter, to change". The Latinised form of the word is tropus.
In music, a trope is adding another section, or trope to a plainchant or section of plainchant, thus making it appropriate to a particular occasion or festival.
From the 9th century onward, trope refers to additions of new music to pre-existing chants in use in the Western Christian Church.
Three types of addition are found in music manuscripts:
The standard Latin-rite ninefold Kyrie is the backbone of this trope. Although the supplicatory format ('eleyson'/'have mercy') has been retained, the Kyrie in this troped format adopts a distinctly Trinitarian cast with a tercet address to the Holy Spirit which is not present in the standard Kyrie. Deus creator omnium is thus a fine example of the literary and doctrinal sophistication of some of the tropes used in the Latin rite and its derived uses in the mediæval period.
In certain types of atonal and serial music, a trope is an unordered collection of different pitches, most often of cardinality six (now usually called an unordered hexachord, of which there are two complementary ones in twelve-tone equal temperament). Tropes in this sense were devised and named by Josef Matthias Hauer in connection with his own twelve-tone technique, developed simultaneously with but overshadowed by Arnold Schoenberg's.
Hauer discovered the 44 tropes, pairs of complementary hexachords, in 1921, allowing him to classify any of the 479,001,600 twelve-tone melodies into one of 44 types.
The primary purpose of the tropes is not analysis (although it can be used for it) but composition. A trope is neither a hexatonic scale nor a chord. Likewise, it is neither a pitch-class set nor an interval-class set. A trope is a framework of contextual interval relations. Therefore, the key information a trope contains is not the set of intervals it consists of (and by no means any set of pitch-classes), it is the relational structure of its intervals.
Each trope contains different types of symmetries and significant structural intervallic relations on varying levels, namely within its hexachords, between the two halves of an hexachord and with relation to whole other tropes.
Based on the knowledge one has about the intervallic properties of a trope, one can make precise statements about any twelve-tone row that can be created from it. A composer can utilize this knowledge in many ways in order to gain full control over the musical material in terms of form, harmony and melody.
The hexachords of trope no. 3 are related by inversion. Trope 3 is therefore suitable for the creation of inversional and retrograde inversional structures. Moreover, its primary formative intervals are the minor second and the major third/minor sixth. This trope contains [0,2,6] twice inside its first hexachord (e.g. FâÂÂGâÂÂB and GâÂÂAâÂÂC and [0,4,6] in the second one (e.g. AâÂÂCâÂÂD and BâÂÂDâÂÂE). Its multiplications M<sub>5</sub> and M<sub>7</sub> will result in trope 30 (and vice versa). Trope 3 also allows the creation of an intertwined retrograde transposition by a major second and therefore of trope 17 (e.g., GâÂÂAâÂÂCâÂÂBâÂÂFâÂÂFâÂÂ|âÂÂEâÂÂEâÂÂCâÂÂDâÂÂBâÂÂA â Bold pitches represent a hexachord of trope 17).
In general, familiarity with the tropes enables a composer to precisely predetermine a whole composition according to almost any structural plan. For instance, an inversional twelve-tone row from this trope 3 (such as GâÂÂAâÂÂCâÂÂBâÂÂFâÂÂFâÂÂDâÂÂCâÂÂAâÂÂBâÂÂEâÂÂD) that is harmonized by the [3âÂÂ3âÂÂ3âÂÂ3] method as suggested by Hauer, will result in an equally inversional sequence of sonorities. This will enable the composer, for example, to write an inversional canon or a mirror fugue easily (see example 1). The symmetry of a twelve-tone row can thus be transferred to a whole composition likewise. Consequently, trope technique allows the integration of a formal concept into both a twelve-tone row and a harmonic matrixâÂÂand therefore into a whole musical piece.
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