There are several different forms of music and in each different genre there is a different aim and thus something different to appreciate.
Folk music is a great place to strengthen, refine and develop an appreciation of different forms of music. Folk music is profoundly refreshing and is a great antidote for those whose taste in music has been jaded by the quality of other pieces of music. In the ballads and songs of folk music musical genuineness can be found from which it is possible to draw strength. In contrast to the professionalism of a more advanced form of music, folk music is child-like in its simplicity. Folk music is an expression of feeling rather than technique and it is this that needs to be appreciated. Folk music also has the advantage of being the acorn from which the oak of classical music has grown. Prodigies like Beethoven were weaned on German folk music before writing their classic symphonies.
The next most complex form of music is the art song. The art song is composed by individuals and written on paper, therefore providing a more complex form of organization. The most successful musicians associated with the art song are Schumann, Schubert, Brahms, Grieg, Wolf and Strauss. Like folk music the art song is meant to convey emotion, but this is given across in a more professional and structured method, removing some of the pure emotion of the art form but in exchange having a higher chance of being a commercial success.
The next evolution in music is the opera or operetta which could not have come into being without the art or folk song. As a cathedral evolves from the architectural progress of smaller buildings, so does the opera or operetta. The opera or operetta has a much more refined structure with more links between the acts of the music than the previous pieces, much like art songs built upon the foundations of folk music. Operas and operettas were developed under the shadow of the church and therefore they had to fit in with the religious dogma that prevailed at that time which had a massive impact on this form of music and also how it should be appreciated. One of the problems of the opera or operetta is that due to the choral nature of the music the individual voice and its emotion is lost among the group. Therefore the music can sometimes be criticized as being impersonal and the audience can begin to feel a form of detachment to the performance, which presumably would not happen with folk music which aims to bring the audience in with clapping and movements.
After the opera and the operetta musical appreciation must move on to more complex forms of art such as piano pieces. Piano music has the potential to convey a wide scope of deep emotions and drama. Piano music only began to reach its full potential in the work of Bach or Beethoven. Especially worth mentioning are Beethoven's sonatas such as Pathétique, Waldstein, Appassionata and Moonlight.
Piano music is especially important for appreciators of music because if people can appreciate the true depth and complexity of piano music then they will easily be able to appreciate all modern instrumental and orchestral music. If a listener can listen to and intelligently analyze and appreciate a Beethoven piano sonata then with practice he or she should be able to evaluate other classical or modern musical pieces such as the string quartet or the symphony orchestra. The piano sonata has become the Rosetta stone or master key to unlocking modern instrumental music. For example, the piano sonata has a beginning, middle and end and each section needs to be evaluated on its own merits within the performance but also the in way the sections fit together as a whole and the story they tell to the audience. More complex forms of music such as the chamber orchestra also try to convey the same elemental structure to the audience, with the beginning, middle and end structure and the overlying narrative. Therefore, just as folk music was the seed for more complex types of music which need to be understood in order to properly appreciate something like the opera and operetta, so piano music is the critical seed from which all other complex instrumental music has grown.