Universal Level of Music
Only a century ago, classical music was able to embrace all music of the time, such as ethnic or jazz music.
Stravinsky:My knowledge of jazz was derived exclusively from copies of sheet music, and as I had never heard any of the music performed, I borrowed its rhythmic style not as played but was written. I could imagine jazz sound, however, or so I like to think. From “The Lives of Great Composers” by Harold C. Schoenberg
In one moment classical music was even more than ever before universally seen around the world as the summit of all musical traditions. Japanese conductor Ozawa could wonder why, as a Japanese, he is dealing with classical music and not with his national Japanese traditional music.
But classical music lost this ability to incorporate current musical activity sometime along XX century. While it continued to officially be viewed as synonym for art music, in reality it became restricted to a genre - the institutionalized genre, that has deep roots, but not anymore a synonym for (art) music. What was being done in movie or pop music was not anymore fitting inside the classical common practice. When one today chooses to be a classical musician, one chooses to work in a restricted frame.
Also, during XX century classical music lost the monopoly on its main defining quality - the depth and variousness of atmosphere.
As with many forms of fine art, classical music often aspires to communicate a transcendent quality of emotion, which expresses something universal about the human condition. While emotional expression is not a property exclusive to classical music, this deeper exploration of emotion arguably allows the best classical music to reach what has been called the "sublime" in art. Wikipedia
For centuries this could indeed been found only in classical music, but during XX century it started to appear elsewhere, like in movie music. Movie music was not only a part of movies for which it was composed, but also introduced some novelties. Movie composers had an approach more based on pure authorship than classical composers ever did. Theirs music introduced previously unknown atmospheric qualities and orchestral finesses, and sometimes also new levels of effectiveness. While still based on classical music, it was somewhat outside of classical frame. This was perceived, and articles appeared discussing the fact that strictly classical criteria could not anymore be applied in measuring the quality of movie music. However, writers could not put their finger on what causes this – for example, it was pointed towards that feature of film music that it has to be instantly liked. But this discourse was already well known in classical music.
So during second half of XX century people were becoming aware that musical art extends beyond what we commonly call classical music. Status of classical music as the art music was becoming more of a license. Many unbelonging, nameless instrumental forms pervaded the century – nor classical, neither pop&jazz, sometimes utilitarian such as movie music, usually connected with electronic instruments. They showed that classical music started to transform from the summit of musical art into a sumptuous relic of the past.
Behind the curtains, this forced musicians and musicologists to seriously rethink that hanging essential question: what is art music?
Obviously, there was a need to talk about art music outside of notions of classical music, and soon among musicologists the difference will be made between art music and more particular classical music. But this didn’t reach consciousness of wide audiences and musicians, who still used terms classical music and art music as synonyms. It was an absurd situation, since movie and synthesizer-based music was often not less artistic than classical. Wide circles of music lovers were unconsciously aware that musical art goes beyond classical music, but this was not consciously discussed. Movie music was weakly covered in literature, while what we today call electronic music remained completely ignored.