forms of musical expression
Because music is a language, it fundamentally cannot be right or wrong, or good or bad. However, the ideas expressed through music can vary in terms of meaning, interest, and complexity; additionally, they can be conveyed more or less effectively. Proficient musicians train so that they are able to most accurately express what they intend without technical inhibitions.
Within music, a plethora of art forms have developed over time with their own unique characteristics and rules; and these can be followed more or less successfully. For example, within Western classical music the objective is typically to learn and recite the works of other composers as closely as possible to their original intentions. In jazz, players strive is to create something new in real time through improvisation and interplay with other musicians. Music can be studied and created in an incredibly broad number of ways, however it is the choice of a specific structure and the establishment of specific norms that give us a framework in which to create and experience meaning.
Within the West, many teachers confuse the arbitrary rules of their art form with objective rules about the language of music as a whole. Because of this, they often convey the idea that these rules constitute the most or only valid way to create music. Consequently, students who struggle adhering to the rules of a specific art form often end up feeling like they are fundamentally incapable of musical expression.
Done in a healthy way, music is not something which should be created primarily for the sake of conformity to external conventions. The musicians who create the music others find most meaningful are those who have a incredibly strong personal connection to the the music, one which runs much deeper the confines of their style. As with any form of art, we are compelled by those who have a message to express that they truly believe in, not necessarily those who follow the rules the best.
Truly effective communication through music draws on an advanced knowledge of the language and its intricacies. However, once you understand musical norms and expectations, you can choose to adhere to or subvert them, depending on what it is that you want to express.