in the process of melody, the undulating lines formed by the change of pitch direction are called melody lines.

Melody lines can be roughly divided into four forms: ascending, descending, parallel and wave-like, and they are developed by means of step-by-step, jumping, jumping, repeating homophones, etc. Generally speaking, ascending melody makes people feel excited, nervous and strengthened, descending melody makes people feel calm, relaxed and weakened, and repeating homophones will make people feel persistent and deepen their memory.

Melody line is equivalent to the concept of line in visual sense to human auditory sense. Melody line is one of the main elements that reflect the thoughts and feelings of musical works.