Adult contemporary music (AC) is a broad style of popular music, ranging from 1950s and 1960s vocal music to predominantly ballad-heavy music with varying degrees of rock influence. The term is also used to describe or categorize radio formats that play such music.

AC radio plays mainstream music, excluding "hip hop", "heavy metal", youth-oriented "hard rock", some "teen pop" music and rhythmic "dance tracks" as they are less popular amongst the target demographic of these radio stations, which is intended for an adult audience. Radio stations playing this format will often target the 18–54 age group, also the demographic that has received the most attention from advertisers since the 1960s.

Over the years, AC has spawned numerous sub-genres: "hot AC", "soft AC" (also known as "lite AC"), "modern AC", "urban AC", "rhythmic AC", "smooth AC" (i.e., smooth jazz), and "Christian AC" (i.e., a softer type of Contemporary Christian music). Some radio stations play only "hot AC", whilst some play only "soft AC"; and then there are others that explicitly play a variety of sub-genres. Therefore, it is not usually considered a specific genre of music; it is merely an assemblage of selected tracks from musicians of many different genres.

Contemporary classical music can be understood as belonging to the period that started in the mid-1970s with the retreat of modernism. However, the term may also be employed in a broader sense to refer to all post-1945 modern musical forms.

Generally "contemporary classical music" amounts to:

At the beginning of the 20th century, composers of classical music were experimenting with an increasingly dissonant pitch language, which sometimes yielded atonal pieces. Following World War I, as a backlash against what they saw as the increasingly exaggerated gestures and formlessness of late Romanticism, certain composers adopted a neoclassic style, which sought to recapture the balanced forms and clearly perceptible thematic processes of earlier styles; see also New Objectivity and Social Realism). After World War II, modernist composers sought to achieve greater levels of control in their composition process (e.g., through the use of the twelve tone technique and later total serialism). At the same time, conversely, composers also experimented with means of abdicating control, exploring indeterminacy or aleatoric processes in smaller or larger degrees. Technological advances led to the birth of electronic music. Experimentation with tape loops and repetitive textures contributed to the advent of minimalism. Still other composers started exploring the theatrical potential of the musical performance (performance art, mixed media, fluxus).