Most music is written in a particular key, and it centers on a tone from which notes rise and fall in a familiar way. In the early 20th century, some adventurous composers wrote pieces that were atonal, such as Arnold Schoenberg, whose atonal compositions are among the most well known, although he objected to the term itself. The word atonal combines a-, "not," and tonal, from the Greek tonos, "pitch, accent, or key."