Accordions have been used in a wide variety of traditional folk music around the world. Accordions, free reed instruments that can be played with either a keyboard or diatonic buttons, provide a multitonal and varied sound that can accompany a voice all on its own. One notable exception to the kind of folk music that features the accordion is bluegrass, a folk style developed in Appalachia that exclusively features string instruments such as the guitar, banjo, fiddle, dobro, and mandolin.

In the early twentieth century, many composers sought to go beyond the traditional eight note scale of Western music. The first composer to set out a system to use atonality in compositions was Arnold Schoenberg, who created a "twelve tone system" in the 1920s of chromatic tones that gave each note equal weight. The system was used heavily by composers after World War II.

The time signature is two numbers, which are stacked one on top of the other and are placed at the beginning of a piece of music. The top number indicates how many beats are in each measure. The bottom number indicates how long each beat will last, with a four meaning a quarter more, and an eight an eighth note.

The clarinet is a woodwind instrument, and produces sound like all woodwind instruments, by the player blowing through a reed and controlling the sound by opening and closing valves with his or her fingers. Every other instrument listed in some way uses a keyboard, or in the case of the organ, multiple keyboards.

Bluegrass is a form of folk music developed in the middle of the twentieth century, primarily in Appalachia. The musical form developed around string instruments, which were available and primarily used in square and barn dances in the region. The clarinet, a wind instrument, is the only instrument listed that is not a key element of bluegrass ensembles.

Jazz was born in nightclubs in cities throughout the south in the early twentieth century. A common problem for early jazz groups was an inability to be heard, and many advancements in amplifying sound were made because of jazz. As such, quieter acoustic string instruments like the mandolin never made a dent in jazz.

In the 1913 Paris Ballet season, the Russian artists Igor Stravinsky, a composer, and Vaslav Nijinsky, a choreographer, debuted the ballet The Rite of Spring. The extremely avant-garde nature of the piece nearly caused the audience to riot. Stravinsky's score played with every convention in music at the time, including rhythm, melody, and dissonance.

John Cage became well known in the mid-twentieth century for his radical and odd compositions. In particular, Cage used odd instruments and strange tunings, and created a piano with objects placed on keys. His most famous work is the completely silent 4'33", which calls for the performer(s) to sit and do nothing for four minutes and thirty three seconds.