Describe the key elements that differentiate a commercially successful pop melody from an ineffective one, focusing on aspects of contour, phrasing, and memorability.

A commercially successful pop melody distinguishes itself from an ineffective one primarily through its contour, phrasing, and memorability. The contour of a melody refers to the shape it creates as it moves up and down in pitch. Successful pop melodies often utilize a balanced contour, incorporating both stepwise motion (moving to adjacent notes) and leaps (moving to notes farther away). These leaps aren't random, but are generally small and followed by movement in the opposite direction, creating a sense of tension and release. For instance, consider the opening melody of "Rolling in the Deep" by Adele. It begins with a relatively stable note, then leaps up, followed by a stepwise descent, creating a sense of drama and resolution within the contour. An ineffective melody might be too static, remaining on the same notes, or be too erratic, with large....