creative work. In Indian classical music, improvisation is a core component and an essential criterion of performances. In Indian, Afghan, Pakistani, and Bangladeshi classical music, raga is the "tonal framework for composition and improvisation". The Encyclopædia Britannica defines a raga as "a melodic framework for improvisation and composition". In Western music Medieval period Although melodic improvisation was an important factor in European music from the earliest times, the first detailed information on improvisation technique appears in ninth-century treatises instructing singers on how to add another melody to a pre-existent liturgical chant, in a style called organum. Throughout the Middle Ages and Renaissance, improvised counterpoint over a cantus firmus (a practice found both in church music and in popular dance music) constituted a part of every musician's education, and is regarded as the most important kind of unwritten music before the Baroque period. Renaissance period Following the invention of music printing at the beginning of the sixteenth century, there is more detailed documentation of improvisational practice, in the form of published instruction manuals, mainly in Italy. In addition to improvising counterpoint over a cantus firmus, singers and instrumentalists improvised melodies over ostinato chord patterns, made elaborate embellishments of melodic lines, and invented music extemporaneously without any predetermined schemata. Keyboard players likewise performed extempore, freely formed pieces. Baroque period The kinds of improvisation practised during the Renaissance—principally either the embellishing of an existing part or the creation of an entirely new part or parts—continued into the early Baroque, though important modifications were introduced. Ornamentation began to be brought more under the control of composers, in some cases by writing out embellishments, and more broadly by introducing symbols or abbreviations for certain ornamental patterns. Two of the earliest important sources for vocal ornamentation of this sort are Giovanni Battista Bovicelli's Regole, passaggi di musica (1594), and the preface to Giulio Caccini's collection, Le nuove musiche (1601/2) Melodic instruments Eighteenth-century manuals make it clear that performers on the flute, oboe, violin, and other melodic instruments were expected not only to ornament previously composed pieces, but also spontaneously to improvise preludes. Basso continuo The basso continuo (accompaniment) was mainly improvised, the composer usually providing no more than a harmonic sketch called the figured bass. The process of improvisation was called realization. Organ improvisation and church music see Category:Organ improvisers According to Encyclopædia Britannica, the "monodic textures that originated about 1600 ... were ready-made, indeed in