This timeline shows the different genres within the scope of "Classical Music"
Medieval music was the first type of music history has a record of. It was influenced greatly by the Pope Gregory and Gregorian chant became prominent. He was the first person to teach a mass of people a simple melody line. Organum was a basic form of harmony, but it was limited to only one or two lines of music. This constricted its uses greatly. This type of music would seem very simple in comparison to today's music.
This was the period of great inspiration and creativity. The greatest amount of freedom was found within harmonies. This was due to the fact that the church was losing its grip slightly, and did not have the influence that it used to. The Renaissance movement was based off a movement in the year 1400 named the ars nova, or rather new art. People were looking for new inspiration and sources of creativity. The music of this time period was predominantly vocal. This was the expansion of music into many different freedoms that had never been seen before within musical boundaries.
During the Baroque Era, orchestras varied the number of instruments that they used. This allowed for a greater tone variance. Many different emotions were being expressed because of this by the composers. Lyrics were also added to add a greater emotional effect. This era is classified by great and sporadic changes in harmony and intervals. Towards the end of the era, this was forgotten and baroque became synonymous with elaborate music. Bach was one of the most well-known composers of the time.
The Classical Period of music is the period most people know of. The big names that stand out include Mozart and Beethoven. Haydn was another composer that stuck out during these times. Enlightenment happened in the eighteenth century, so the in the time period of this era. This caused musicians and composers to look for the future that was more influenced by scientific theories than that of the church. Music became more logical and balanced than that of change characteristic of the Baroque Era. The creation of instruments was also expanded on and many more people were able to play. Standardized symphonic orchestras also became more common, and generally had a set number of instruments in each. The cliché "dada-da-dummmm" of Beethoven's fifth symphony is still what defines this era centuries later.
The Romantic Era was greatly different than that of the Classical Period. Instead of having the formal symphonies of Mozart, Beethoven, and Haydn, new sources of inspiration were found. These included many different human emotions and past literature. Traditional structures for melody were forgotten and simply expressing human emotion became dominant. Franz Liszt was one of the main composers of time, and he also liked to include "sounds" within his music. He also popularized rhapsodies that were based on Hungarian Gypsy music. This age related music to current events and literature as it had never been done before.
The Modern Era increased the amount of freedoms that was in music to unimaginable heights. Dissonance was greatly more prominent than what it was in any other time period. One ballet, "The Rite of Spring" caused riots because of the dissonance that was used. People thought that the composer, Igor Sravinsky, was attempting to destroy music. Mahler is one of the leaders of modern times. His music pushed the limits on range, keys, and harmonies in general. Mahler's symphonies could last hours and require extremely large orchestras. New instruments have been added and digital effects layered over existing instruments. Composers wrote music including some of these newer sounds. Music will continue to evolve and more era will be created, but for now, these are the periods of what we call "classical music."