Classical music is primarily a written musical tradition, preserved in music notation, as opposed to being transmitted orally, by rote, or in recordings. While there are differences between particular performances of a classical work, a piece of classical music is generally held to transcend any interpretation of it. The use of musical notation is an effective method for transmitting classical music, since the written music contains the technical instructions for performing the work. The written score, however, does not usually contain explicit instructions as to how to interpret the piece in terms of production and/or performance, apart from directions for dynamics and tempo; this is left to the discretion of the performers, who are guided by their personal experience and musical education, their knowledge of the work's idiom, and the accumulated body of historic performance practices. Classical music is meant to be experienced for its own sake, unlike music that serves as an adjunct to other forms of entertainment (although orchestral film music is occasionally treated as classical music). Classical music concerts often take place in a relatively solemn atmosphere, and the audience is usually expected to stay quiet and still to avoid distracting the concentration of other audience members. The performers often dress formally, a practice which is taken as a gesture of respect for the music and the audience, and performers do not normally engage in direct involvement or casual banter with the audience. Private readings of chamber music may take place at more informal domestic occasions. Its written transmission, along with the veneration bestowed on certain classical works, has led to the expectation that performers will play a work in a way that realizes in detail the original intentions of the composer. Indeed, deviations from the composer's instructions are sometimes condemned as outright ethical lapses. During the 19th century the details that composers put in their scores generally increased. Yet the opposite trend"”admiration of performers for new "interpretations" of the composer's work"”can be seen, and it is not unknown for a composer to praise a performer for achieving a better realization of the composer's original intent than the composer was able to imagine. Thus, classical music performers often achieve very high reputations for their musicianship, even if they do not compose themselves. Classical composers often aspire to imbue their music with a very complex relationship between its affective (emotional) content, and the intellectual means by which it is achieved. Many of the most esteemed works of classical music make use of musical development, the process by which a musical germ, idea or motif is repeated in different contexts, or in altered form, so that the mind of the listener consciously or unconsciously compares the different versions. The classical genres of sonata form and fugue employ rigorous forms of musical development. (See also History of sonata form) Another consequence of the primacy of the composer's written score is that improvisation plays a relatively minor role in classical music, in sharp contrast to traditions like jazz, where improvisation is central. Improvisation in classical music performance was far more common during the Baroque era than in the nineteenth and twentieth centuries, and recently the performance of such music by modern classical musicians has been enriched by a revival of the old improvisational practices. During the Classical period, Mozart and Beethoven sometimes improvised the cadenzas to their piano concertos (and thereby encouraged others to do so), but they also provided written cadenzas for use by other soloists.