Principles include mastery of knowledge and skills, creative expression, etc. , and methods include observation and feedback.

1. Evaluate whether students have mastered the basic knowledge and skills of music, including music theory knowledge, playing skills, music performance, etc.

2. Evaluate whether students have creative thinking and expressive force, and whether they can show their own characteristics and styles in music creation and performance.

3. Evaluate students' skill level and performance ability by observing their performances and performances.

4. Help students to improve and improve their musical performance ability by providing students with feedback and opinions.