20th Century Music: the Experience
Impressionsim
Jazz and pop
Composers
Debussy 
Ravel 
Gamelan influences
In the Paris World Conference Exhibition of 1889, Debussy the Indonesian gamelan music for the first time, and was deeply intrigued by it. Eventually, he wrote "Pagodes", an impressionist work that has many gamelan influences. For example, the gong in gamelan music is represented by the open fifths in the left hand of the piano.
Contextual knowledge
The industrial revolution enabled people to move around the world more easily, making ideas no longer bound or limited by geographical location. Musical ideas could now be spread and influenced all over the world.
Example: Debussy and gamelan music. Debussy was a French composer; how could he have been influenced by traditional Indonesian music?
What is impressionism in music?
Musical style initiated by Claude Debussy towards the end of the 19th century.
The term 'impressionism' originated from a style of French painting. These paintings don't often have very loud colours or definite strokes, essentially creating a very vague picture that shows the atmosphere of the scene.
Some examples
"Impression, Sunrise" by Claude Monet 
"Woman with a Parasol" by Claude Monet 
This piece is another example of Debussy's impressionist works. In the piece, Debussy creates an empty, desolate atmosphere with certain imagery to present a sunken cathedral at the bottom of the ocean to us.
For example, in bar 1 of the piece, Debussy uses parallel fifths and octaves to create the atmosphere of a spacious but empty are that seems cold and desolate. (See next text box for picture)
Unlike Debussy, Ravel's impressionist works tend to be more virtuosic and are slightly less minimalistic. One such example can be found in "Miroirs"
In this piece many running notes are played in order to convey a sense of flowing and dreaminess. Such techniques would require a certain amount of virtuosity, but at the same time, it has to be subtle and quiet. The piece only requires such skills, but isn't completely meant to show it off.
Despite disliking the impressionist painting style, Debussy seemed to create a music genre that had similar features. Rather than focusing on the definite details, the music was meant to create an atmospherical sense that gave a vague idea of what it was about. In more technical terms, the harmony is more "static", there is more emphasis on "instrumental timbres that [create] a shimmering interplay of 'colours'," its melodies "lack directed motion, surface ornamentation that obscures or substitutes for melody, and an avoidance of traditional musical form".
These all help the audience to focus on the bigger picture, which is the sense and the atmosphere of the entire piece, rather than the small, definite details of the piece. One such example is time signatures. Ravel often used many time signature changes in order to prevent the audience from being able to predict everything definitely.
In Miroirs, for example, these many running notes, together with the time signature changes and rubato, are used to make the audience think less definitely about the piece, and just go along with the flow.
Early jazz and impressionist have also been said to influence each other.
Harmony
Impressionist music used much extended harmonies, including other scale degrees such as 9ths and 13ths into chords
This is also a technique in harmony commonly used in jazz
such as this excerpt of The Sunken Cathedral by Debussy 
In fact, one of the defining traits of jazz is its extended harmonies that create a unique colour to the genre
Here is an example of a very famous jazz piece: AUTUMN LEAVES - Frank Sinatra
This piece utilises 7th and 9th chords extensively, using them to create the unique jazz harmonies that make up its genre. If not for these extended chords, the piece simply would have been any other standard song with lyrics!
Debussy and Ravel were also exposed to some pre-jazz in the 20th century like ragtime.
pieces written by them such as Ravel - Piano Concerto in G Major and Debussy: Golliwog's Cakewalk show evidences of this
the freedom in the rhythm and its syncopation that are also present in jazz can be found in these pieces.
One of the defining traits of ragtime is its freedom in its rhythm and its syncopation, creating this sense of groove that the listeners can enjoy. Hence, the rhythmic aspects of these pieces make it very clearly related to ragtime and its own sense of rhythmic freedom.
POP
From here, the "pop" industry, or popular music, was born.
One of pop music's own defining traits is its rhythm and syncopation that makes the music so "groovy" and "catchy", according to what some might say. Because we all have a tendency to want to hear things on the downbeats and strong beats, by purposely syncopating the rhythms, it causes us listeners to want to subconsciously create our own beats on the downbeats and strong beats to make up for the missing ones in the music. This could be why when we listen to pop or jazz music, we tend to tap our feet in time with the music, and dancing to them freestyle can be so easy and natural to most.
LYRICS
Lyrics is something else both pop songs and jazz works have in common. Lyrics play a big role in these songs, and there are even times when people listen to these songs for the lyrics, not for the music. The 20th century was a time when people broke free of conventional rules of music holding them in place, giving composers, jazz and pop musicians alike the power to express their own individual thoughts as much as they wanted. In the Baroque and Classical period, songs for singers may have been composed for operas and love stories. However, in the pop and jazz industry, the lyrics are more personalised according to the own singer/musician's life experiences, giving the audience a lot more opportunities to relate to the artists more. This, in fact, is what makes some of these songs so successful.
Example: All Too Well by Taylor Swift this is one of the songs that best shows Taylor Swift as a songwriter. She poured her heart and soul out into this song, in fact even making it 10 mins long initially such that she had to cut it down by a lot. Even thought there's nothing that spectacular in the music arrangement or the singing, it's the lyrics that caught the attention of fellow heartbroken people that needed someone who could relate to their situations.
Example: One Last Time by Ariana Grande in this song, there is a repetitive line that plays in the accompaniment throughout most of the piece that is very clearly syncopated. In addition to providing harmony, this line sets up the rhythmic syncopation in the piece, making any listener want to tap their foot or groove to it.